Evolver now imports management modules for any apps before any

signals are emitted. This gives apps a chance to perform any operations

needed during the syncdb/migration/evolution process, such as

registering entries in the database. Normally, the syncdb and

migrate commands will do this automatically, and we're guaranteeing

that it'll happen even if evolving programmatically through the

Evolver.

Unit tests pass.
Tested against Review Board. Saw that our management modules were able

to connect to signals and respond to them.