model source subscription
add migration to the liquibase script

Use a liquibase custom task update to fix bad data prior
to moving to the table with constraints.
allow single subscriptions to be refreshed

Conflicts:
	src/test/java/org/candlepin/controller/PoolManagerTest.java
Update refresh pools for owner to clean up pools that exist for other owners
Output logging to liquibase logs.

Log via liquibase logger so that it shows up in the
liquibase output. By default, log via System.out
Merge pull request #560 from candlepin/mstead/log-custom-task-to-liquibase

Output logging to liquibase logs.
Adding spec test for refresh_pools migrate case
Flush the entity manager when we delete a pool.

The deletes weren't executed until later, so creating new pools
still caused a constraint violation exception.

Also remove useless exception handling.  It's better to let the
refresh fail and rerun anyhow
Added another test case around migration
Merge pull request #558 from candlepin/ckozak/source_subscription

Ckozak/source subscription

ACK