abrt: refactor file contents loading

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Richard Marko <rmarko@redhat.com>
abrt: Use pkg_* files to determine package information

Closes #76.

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