Update Database/Query test case to use fixtures.

Using fixtures means the test case doesn't need to create tables or
insert records.
Add update + join support.

This currently only works in MySQL. Additional work will be needed to
make it work with postgres + sqlite.
Fix failing test.

Columns were removed from the fixtures in a previous set of changes.
Update this test to reflect that.
Add basic table level updates.

Add basic table level updates that can update multiple records. Don't
implement _matchRecords or other join workarounds as they often lead to
concurrency issues. We can revisit that functionality later on if
necessary.
Rename method to match 2.x method.

update() is a handy method that I don't want to use just yet.
Add update with join support for Postgres.

Postgres requires some query fudging to make joins with updates
syntactically valid. Add a query translator that moves joins around and
creates a 'from' clause.
Enforce consistent ordering

Fix cross DB test failures caused by ordering and cross join issues.