Updated an inaccurate comment.

Tests can run nearly as fast under PostgreSQL and MySQL as under SQLite
with a bit of configuration and the speedup is always a good thing.
Moved test_templates to templates to prevent issues with regressiontests/templates later on.
Removed __init__.py files.
Merged regressiontests and modeltests into the test root.
Adjusted runtests to the new layout.
Adjusted coveragerc
Renamed some tests and removed references to modeltests/regressiontests.
Renamed a template to be found by the loaders.