[Owncloud] Changing the database backend

[Bart Visscher]

Hi,

I pushed a branch doctrine, in it is the first conversion of the DB
backend to the Doctrine database access layer (DBAL). The DBAL supports
changing the schema so we don't need MDB2 for that.
The plan is to remove MDB2 and our PDO layer, and only use Doctrine for
database access.

Are there any objections to this? When there are no objections i will
merge this after our meeting in Berlin.

Bart