Make wikimetrics' database setup depend on alembic

Wikimetrics's database setup relies on alembic being around. So we
make the setup dependent on install_wikimetrics_dependencies and
thereby puppet makes sure alembic is available to setup the database.

To keep the order of operations, we move the ::wikimetrics::database
after its requirements.

Change-Id: I93ed7245d8c2f8e437dd7eb5643b7416d78a1f8b
Merge "Make wikimetrics' database setup depend on alembic" into production