Add metadata, totalcount fields to zones/recordsets collections

*Adds a metadata field to API calls if there is metadata
*Adds objects.base.PagedListObjectMixin to hold metadata fields
*Adds a count_x call to domains/recordsets _find_x to get data
*Unit tests for metadata/total_count

Change-Id: I6929e933afad1570603e9276ccf33cf45bb349d3
Implements: blueprint zones-and-record-totalcount
Merge "Add metadata, totalcount fields to zones/recordsets collections"