abrt-configuration: install XML interface files

Related #750

Signed-off-by: Jakub Filak <jfilak@redhat.com>
abrt-configuration: fix problems uncovered in the review

- use ARRAY_SIZE macro
- configuration_new() makes a copy of arguments itself
- die if no configuration interface was loaded

Related to #750

Signed-off-by: Jakub Filak <jfilak@redhat.com>
spec: install Configuration D-Bus XML interface files

Related to #750

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