[FOR REVIEW] Autotest frontend database layer changes

Folks,

It's been quite a journey, but the database work to modernize has
come to a milestone.

For those not aware with the changes, we're dropping a lot of
custom code, both database migration related and SQL DDL as well.
The new way of creating and managing the autotest database is 
via Django and Django's South extension only.

For reference, this has been initially discussed on github issue
#589, but we've come a long way from the initial proposals there.

New installations should not notice any hiccups, and extensive
testing has been done using ./contrib/install-autotest-server.sh.

For existing installations, migrations instructions will be posted
to the WIKI shortly.

Please test and report your feedback!

Thanks!
CR.