Right now SapphireTest::objFromFixture() requires a class as the first
argument. This is fine when your fixture file uses classes as the keys,
but if populating a fixture via tables, objFromFixture() won’t work.
This patch lets you specify either the table name or the class name as
the key.
The benefit here is that you can build fixtures as raw inserts, which is
substantially quicker, and is likely to be a useful tool in building
more efficient test suites.
