pkgman: fix for syntax (help)

The tool "pkgman" was not showing it's help text
and this seems to be somehow related to the
initialization of constants such as
"kCommandCategoryPackages"; these values seems to
be coming through as empty-string for some reason.
I am changing those to be "#define" of regular
C-Strings and this seems to resolve the problem.
These values only seem to be used to group the
possible commands for production of the syntax or
help text - there do not seem to be any deeper
impacts beyond that functionality.

Change-Id: If9cd61462cd7f1f1b5ab2ece521bb3f00a1ba246
Reviewed-on: https://review.haiku-os.org/c/1139
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

[pkgman] pkgman informs if package is already installed.

While installing packages through pkgman, it will inform if specific
package is already installed. Fixes #12447 : [pkgman] inform if a
package is already installed.
Change-Id: I194bc849c42ba52a696a6cb52d87aebaff530f35

pkgman: Add --debug option for most commands

* Add CommonOptions class and add an instance to Command. It supports a
debug level.
* full-sync, install, search, uninstall, update: Add option --debug.
This allows getting some debug output from the solver in cases where
the result seems weird.

pkgman: Update some user messages

pkgman [un]install/update: Add non-interactive mode (-y)

Remove /boot/common for good

* Remove support for the "common" installation location from packagefs,
package kit, package daemon, package managers.
* Rename the B_COMMON_*_DIRECTORY constants referring to writable
directories to B_SYSTEM_*_DIRECTORY.
* Remove/adjust the use of various B_COMMON_*_DIRECTORY constants.
I'm sure some occurrence still remain. They can be adjusted when the
remaining B_COMMON_*_DIRECTORY constants are removed.

Refactor reusable pkgman code into libpackage

* Move RepositoryBuilder class to libpackage and add B* prefix to name.
* Pull BPackageManager class out of PackageManager and move to
libpackage. The base class is customizable via three handler objects
responsible for transaction handling, request execution, respectively
user interaction.
* Reorganize _ApplyPackageChanges(): Now we first prepare the
transactions for all affected installation locations (downloading
files etc.) and then commit them.

pkgman: add support for [un]installing/updating in system

pkgman: auto-refresh repositories only for update/install

pkgman: PackageManager: Use flags instead of bools in ctor

pkgman [un]install: fix option '-H'

pkgman: Organize commands by category

pkgman install: Fix typo in usage text

pkgman: Refactoring -> PackageManager

Move common and reusable functionality from "search" and "install" to
new PackageManager class.

pkgman install: Simplify transaction creation

pkgman install: Add problem solution selection support

pkgman install: Refresh repositories first

pkgman install: better out-of-memory error messages

pkgman install: Complete basic functionality

Download package files to install from the respective repositories and
use BDaemonClient to perform the package de-/activation. Still missing
is the interactive problem solution support.

pkgman: Add beginnings of the "install" command

So far it only solves the dependencies and prints the result. No
problem handling, no actual installation.

pkgman: Add --debug option for most commands

* Add CommonOptions class and add an instance to Command. It supports a
debug level.
* full-sync, install, search, uninstall, update: Add option --debug.
This allows getting some debug output from the solver in cases where
the result seems weird.

pkgman: Update some user messages

pkgman [un]install/update: Add non-interactive mode (-y)

Remove /boot/common for good

* Remove support for the "common" installation location from packagefs,
package kit, package daemon, package managers.
* Rename the B_COMMON_*_DIRECTORY constants referring to writable
directories to B_SYSTEM_*_DIRECTORY.
* Remove/adjust the use of various B_COMMON_*_DIRECTORY constants.
I'm sure some occurrence still remain. They can be adjusted when the
remaining B_COMMON_*_DIRECTORY constants are removed.

Refactor reusable pkgman code into libpackage

* Move RepositoryBuilder class to libpackage and add B* prefix to name.
* Pull BPackageManager class out of PackageManager and move to
libpackage. The base class is customizable via three handler objects
responsible for transaction handling, request execution, respectively
user interaction.
* Reorganize _ApplyPackageChanges(): Now we first prepare the
transactions for all affected installation locations (downloading
files etc.) and then commit them.

pkgman: add support for [un]installing/updating in system

pkgman: auto-refresh repositories only for update/install

pkgman: PackageManager: Use flags instead of bools in ctor

pkgman [un]install: fix option '-H'

pkgman: Organize commands by category

pkgman install: Fix typo in usage text

pkgman: Refactoring -> PackageManager

Move common and reusable functionality from "search" and "install" to
new PackageManager class.

pkgman install: Simplify transaction creation

pkgman install: Add problem solution selection support

pkgman install: Refresh repositories first

pkgman install: better out-of-memory error messages

pkgman install: Complete basic functionality

Download package files to install from the respective repositories and
use BDaemonClient to perform the package de-/activation. Still missing
is the interactive problem solution support.

pkgman: Add beginnings of the "install" command

So far it only solves the dependencies and prints the result. No
problem handling, no actual installation.