gen-tarball: Repackage release tarball of breeze

Instead of cloning the breeze repo and creating a local commit removing
the wallpapers and cursors the official release tarball is downloaded
and repackaged without the wallpapers and cursors. The version number
is kept (so that one knows which version the package corresponds to)
and "-g10" is appended (as done for bzip2) to avoid confusion with
the official release tarball.

The references to the removed wallpapers and cursors in the
CMakeLists.txt file need to be removed/patched out when building the
package. This is done so that our stripped package is identical to the
official release package except for the removed wallpapers and cursors.