Invalid query parameters cause internal server error

[KasperBrandt]

  File "akvo/rest/filters.py", line 61, in filter_queryset
    queryset = getattr(queryset, param)(**args_or_kwargs)

In the new API filtering, you get an internal server error when the query is not correct, e.g.: http://rsr.akvo.org/rest/v1/project/?filter={'incorrect':'code'}.

We should catch this and return the error message in a dict with detail as key. E.g. {detail: 'Related Field got invalid lookup: incorrect'}

[damienallen]

Test plan

Attempt API call with invalid filter. Error should now appear as "detail" in API view.