We have a few tasks that must be completed during an install or upgrade.

One is to register new SCMTools, and the other is to update the version

stored in the siteconfig.
With Django 1.6 times, we'd accomplish these by registering

post_syncdb signal handlers that would execute the necessary database

code, which made sense initially, but it meant that we had little

control over the order of operations. It also wasn't future-proof.
Given how installs/upgrades work now, we'd never get the equivalent

modern signals if we didn't need to perform a database upgrade. We'd

determine that no changes were made to the database, and simply skip the

process that would ultimately emit the signal.
Now, we have a dedicated function and signal for post-install/upgrade

steps. This registers SCMTools, updates the version in the database,

and emits a signal for any further tasks.
This is called both by rb-site and manage.py upgrade. It will not

be called with a simple evolve --execute.
A new manage.py createdb command has been added to help with the

installation side of this for development servers.

Tested creating and upgrading sites using rb-site. Verified the

resulting database entries.
Tested creating using manage.py createdb. Verified the database

entries.
Tested upgrading using manage.py upgrade. Verified the database

entries.
Unit tests passed.