addon-python3 doesn't require addon-python

- abrt-action-analyze-python moved to abrt package
- uses Python3 type (analyzer)
- added python3_event.conf & docs

Related to rhbz#1047085

Signed-off-by: Richard Marko <rmarko@redhat.com>
spec: addon-python3 doesn't require addon-python

Related to rhbz#1047085

Signed-off-by: Richard Marko <rmarko@redhat.com>