Add test dataobject for relationship traversal tests
Add fixture for relationship traversal tests
Add relationship traversal tests

Includes:
- test for valid relation with results
- test for valid relation with no results
- test for invalid relation
Add a test for non existent resource id
Implement aliases for relation names
Add ability to traverse many_many relations
Remove some unneeded comments
Allow for filtering and sorting relation lists
Add pagination to relation lists
Add error message for non existent relation
Add metadata element to relation list results
Refactor applyFilters method

- remove $className argument
- get className via DataList->dataClass
Refactor how limit, offset, sort, and order variables are set
Refactor how totalCount is set
Refactor  references to
Refactor setting meta data into a single method
Switch  and  to private
Add flush and flushtoken to reserved get variables in APIFilter
Allow for filtering on ID field
Refactor RestfulServerV2 code out into APIRequest