Updates to work with PHPCR

This PR does some updates to have the Media object work with PHPCR. 

See also https://groups.google.com/forum/?fromgroups=#!topic/symfony-cmf-devs/l8d9te56r6s

Remarks:
* the Gallery is not updated in this PR.
* also the PHPCR/MediaManager.php contains a hack for the findBy and findOneBy that still needs to be solved
* some templates are updated to use the admin.id method for the id parameter when generating url's, this fixes for PHPCR to use no leading "/", there are some templates left (pixlr) that could not be fixed this way.  The urls in these templates will not work at moment for PHPCR