Enhancement: Add "a" and "l" filter for grappa queries

This PR adds the namespace filters "a" and "l" for grappa queries.
With no filter will look into primary and e-groups, with "a" will look
into primary/secondary/service/e-groups and with "l" will look into
lightweight accounts.


https://github.com/cs3org/reva/pull/1887
https://github.com/cs3org/reva/issues/1773
