JPA persistence binding

Please review.
Included are libs for PostgreSQL, Apache Derby and MySQL.
Tested on PostgreSQL and Apache Derby. Working OK on my production system.

hmm … adding the specific db drivers to the JPA bundle doesn't feel very "generic". Shouldn't we better move them to bundle fragments? @kaikreuzer there were some discussion around why we've finally added the lib directly to the mySQL Service rather than provided a bundle fragment for it. Did you remember the reason?