APY-8 : Implement X-Filter as external server

Small adjustments.
Merge remote-tracking branch 'sourcefabric/apy-8-implement-x-filter' into apy-8-implement-x-filter

Conflicts:
	plugins/superdesk-country/superdesk/country/api/country.py
	plugins/superdesk-country/superdesk/country/impl/country.py