Clean up settings now that graphite requires Django>=1.4

``DATABASE_*`` is no longer relevant.

Also removed some compatibility code for older Django versions than 1.4.
Syntax fix
Merge pull request #512 from brutasse/fix/database

Clean up settings now that graphite requires Django>=1.4
Merge remote-tracking branch 'upstream/master' into feature/tox

Conflicts:
	docs/config-local-settings.rst