Research identity plugin

[RWOverdijk]

@bakura10 pointed out the following on IRC:

[9:23pm] Bakura: RWOverdijk: (!$this->zfcUserAuthentication()->hasIdentity())
[9:23pm] Bakura: do you still need the zfcUserAuthentattion ?
[9:23pm] Bakura: Starting from ZF 2.1, there is a built-in helper for that

This is worth researching.

[RWOverdijk]

Also consider moving setting author on entity to service.