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: Handle -y argument to "drop-repo" command.

Found by -Werror=set-but-unused.

pkgman: Organize commands by category

pkgman: Make use of BRequest::Process()

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.

more work on package kit:
* rip BRepositoryHeader out of BRepositoryConfig and add support
for it to BRepositoryCache
* implement repository removal
* some minor cleanups


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40290 a95241bf-73f2-0310-859d-f6bbb57e9c96

pkgman: Organize commands by category

pkgman: Make use of BRequest::Process()

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.

more work on package kit:
* rip BRepositoryHeader out of BRepositoryConfig and add support
for it to BRepositoryCache
* implement repository removal
* some minor cleanups


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40290 a95241bf-73f2-0310-859d-f6bbb57e9c96