debian: Properly package the python bindings.

debian: Properly package the python bindings.

Build-depend on python-support. Add binary package
python-ceph, making it contain all the ceph python
packages, regardless of their name; the modules are
too small to deserve their own debs.

Make python-ceph depend only on librados2 for now.
librgw is not packaged yet.

Dropping unnecessary build-dep on python-dev, that's
only needed for compiling C extensions, and we're using
ctypes.

Signed-off-by: Tommi Virtanen <tommi.virtanen@dreamhost.com>