Multi DB with tests

This fails miserably due to #8. Will come back later to work out a fix.
Implement multi-DB fix with some hacking

Try to mimic https://github.com/moskytw/mosql/pull/26 without upstream support.

1. Merge branch 'master' into multi_db.
    Conflicts:
	    testproject/djangomosqltest/tests.py
    	testproject/testproject/settings.py

2. Introduce djangomosql/patches.py and rewrite query generation in MoManager accordingly.

=======
WARNING
=======

This version does not work flawlessly with PostgreSQL; group_by induces a

    ProgrammingError: "id" must appear in the GROUP BY clause or be used in an aggregate function.

Other functionalities seem to work. Will need to fix the problem before merging this back to master.
Simpler expect format
Fix group_by syntax generation
Merge branch 'multi_db'

Fix #8