Upgrading to grails 2.4.x, Hibernate4, etc.

This has required a few changes to a few things, in order to make it work.

The only remaining tests which don't pass, are the taglib tests...
Fixes to improve functionality and performance with Hibernate / DB Storage.

* Rewrote DBContainerWorker to respect persisten collections rather than whacking them every time you save.
* Use cascade to handle image deletes (and collection management methods like 'clear()') rather than ham-fisted hacking of collections.
Clear out the configuration for each test, Thanks Grails 2.4 for your Holders thing.
Merge pull request #1 from bvarner/grails24update

Grails24update