Moves test fixtures from tests/validators/ to tests/
Incremental commit - overnight changes

Tests in subdirectories of /modularodm/tests/ have been written or
reviewed by me. Tests in /modularodm/tests/ were written by Nan or
Melissa, and I have not fully reviewed them if they pass.

If those tests fail, I fix them and/or refactor them as necessary
and move them to a subdirectory as appropriate. If it is not immediately
apparent what they are testing, I skip them.
Tests deleting an object from a ForeignField
Renames "1:n" tests to "n:n"
Adds (failing) tests for modifying backrefs on the remote object
Renames 1:1 tests to 1:n
Adds tests for assignment to and deletion from 1:n ForeignFields
Adds test for assignment by index of a ForeignList
Adds test for the "in" operator on ForeignList fields
Adds a (failing) test for inserting a new object into a ForeignList field.
Adds (failing) test for removing an object from a ForeignList via the .remove() method.
Removes __init__.py - subdirectories of /tests/ need not be modules.
Merge pull request #28 from lyndsysimon/feature/backref_tests

ForeignField tests