Add support for module ordering

Module order is supported when returning modules in both serialize (for
the admin system) and spotlightify (for the frontend system).

This commit includes adding modules through the /dashboard route but
does NOT include updating existing modules. At the moment this will
raise a NotImplementedError.
Add module ordering to spotlight_config_migration

Simply orders the mgirations in the order in which they are listed in
the existing config.

Conflicts:
	stagecraft/apps/dashboards/lib/spotlight_config_migration.py