[#415] Add AkvoOrganisationParser. Add authentication to viewsets.
[#415] Add AkvoOrganisationParser. Add authentication to viewsets.

The AkvoOrganisationParser is the class responsible for turning the
organisation XML into a python data structure that rest_framework can
handle and create/update organisations from.

akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr