removed database_cleaner (not doing anything relevant)
added datamapper and activerecord to the spec helper and made rake task general (first step for trying to run all the specs simultaneously)
rewrote a lot of the loading so that it is checked at runtime for which ORM one needs to load stuff

- currently having issues with datamapper, whose hooks are being executed in an unexpected context
- need to do the same thing for the various queues
replaced mysql for sqlite3 (easier and faster for tests)
reworked the insertion of queue engine extensions so it can be done and undone (insertion and removal of extensions at runtime, how good). 

Still having problems running the specs alltogether. Where I used to have conflicts between the engine extensions, I can't set the engine for each separate block (at least the way I'm doing it now)