can now use custom repo filters for enabling repos, related abrt/abrt#688

fixed default repository search pattern
this patch now also depends on previous patches "[LIBREPORT PATCH 1/2] fixed exception handling - closes #173" and "[LIBREPORT PATCH 2/2 v2] add docstrings, remove global variable - related #171"

Signed-off-by: Petr Kubat <pkubat@redhat.com>
Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>