ChangesetTooltipAction.findChangeSet() eagerly creates cruRevisions

This means that a simple mouseover on a large ChangeSet can bring Crucible to its knees, because for an N-revision changeset, up to N cruRevisions and N storedPaths are added to CRU_DB through the singleton Hibernate session, blocking all review creation until completed.

Consider for a 2.4.x release

Suggested solution:

1. remove the revision rollout on the tooltip - at most we want to know how many revisions?
2. audit the subclasses of Source - if RepositorySource is the only changesetCapable subclass, consider avoiding source altogether and asking FishEye directly for this info (careful consideration of cs tooltip support in Crucible-only needed here)
3. add either a changeset revision counting method to Source,documenting a contract of speedy return. Or add a getChangesetDescription() that returns a ChangeSetDescription object providing summary data?
4. Bonus refactor: rename Source to RevisionProvider or something. Don't forget subclasses.