packaging: cleanup

- Drop requirement on GCC for having gettext support,
  we're using Python.
- Drop PACKAGE_MAVEN_VERSION, we're not using maven
- Updated POTFILES list

Change-Id: I954c093617fc615fce259c1af0e94f6cfc09b1f5
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>