Incompatible with doctrine/orm 2.7.3

[haltuf]

New patch version of doctrine/orm 2.7.3 brought BC with this commit:
doctrine/orm@d95e03b#diff-b5d0ee8c97c7abd7e3fa29b9a27d1780

The thing is, whole Doctrine\Common\Persistence moved to Doctrine\Persistence namespace.

Proposed sollution: enforce using only new doctrine packages with reference to Doctrine\Persistance, change all classes from Persistence to new namespace in kdyby.