added doxygen support for generating api docs closes #614

Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>
spec: bundle the docs to the -devel package related to #614

Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>