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 resolve-dependencies: Add --debug option

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 resolve-dependencies: Remove bogus option

pkgman: Organize commands by category

pkgman resolve-dependencies: Allow specifying multiple packages

pkgman: C++-ify the command handling

There's now a Command class that must be derived and registered with
a CommandManager, all simplified by a REGISTER_COMMAND macro. That gets
rid of the print_command_usage_and_exit() function copy for every
command, moves the short usage texts to the command implementations,
and avoids any repetition of the command name. When implementing a new
command only a new source file needs to be created, nothing else needs
to be touched.

Rework SolverPackageSpecifier

* It no longer consists of a BPackageResolvableExpression and a
repository. Instead it can now either refer to a package directly or
consist of a search string.
* SolverPackageSpecifierList: Add AppendSpecifier() convenience
versions.
* Adjust LibsolvSolver and pkgman accordingly.

pkgman: Move some classes into own file for reuse

Namely RepositoryBuilder and PackageInfoErrorListener.

pkgman resolve-dependencies: Improve usage text formatting

pkgman resolve-dependencies: Avoid code duplication

pkgman resolve-dependencies: Print package paths

... instead of package name and version. The command should now
work as required by haikuporter.

pkgman resolve-dependencies: Verify result

* Make sure that the computed dependencies don't themselves depend on
the specified package.
* Print only the actual dependencies, not the specified package.

pkgman: Simplify and rename resolve-build-dependencies

* Now it only gets a package (info) file and a single list of
repository directories, optionally with priority, and resolves the
package's dependencies. The more complex two resolving steps it did
before can just as well be done by haikuporter, and this way the
command is more flexible.
* Rename to resolve-dependencies.
* Some TODOs still remain.

pkgman resolve-dependencies: Add --debug option

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 resolve-dependencies: Remove bogus option

pkgman: Organize commands by category

pkgman resolve-dependencies: Allow specifying multiple packages

pkgman: C++-ify the command handling

There's now a Command class that must be derived and registered with
a CommandManager, all simplified by a REGISTER_COMMAND macro. That gets
rid of the print_command_usage_and_exit() function copy for every
command, moves the short usage texts to the command implementations,
and avoids any repetition of the command name. When implementing a new
command only a new source file needs to be created, nothing else needs
to be touched.

Rework SolverPackageSpecifier

* It no longer consists of a BPackageResolvableExpression and a
repository. Instead it can now either refer to a package directly or
consist of a search string.
* SolverPackageSpecifierList: Add AppendSpecifier() convenience
versions.
* Adjust LibsolvSolver and pkgman accordingly.

pkgman: Move some classes into own file for reuse

Namely RepositoryBuilder and PackageInfoErrorListener.

pkgman resolve-dependencies: Improve usage text formatting

pkgman resolve-dependencies: Avoid code duplication

pkgman resolve-dependencies: Print package paths

... instead of package name and version. The command should now
work as required by haikuporter.

pkgman resolve-dependencies: Verify result

* Make sure that the computed dependencies don't themselves depend on
the specified package.
* Print only the actual dependencies, not the specified package.

pkgman: Simplify and rename resolve-build-dependencies

* Now it only gets a package (info) file and a single list of
repository directories, optionally with priority, and resolves the
package's dependencies. The more complex two resolving steps it did
before can just as well be done by haikuporter, and this way the
command is more flexible.
* Rename to resolve-dependencies.
* Some TODOs still remain.