[RFC] Drop controller plugin and view helper

[adamlundrigan]

I propose we drop the controller plugin and view helpers bundled with ZfcUser.

Rationale:

• ZF2 already provides a bundled identity view helper and controller plugin that render zfcUserIdentity redundant.
• zfcUserDisplayName has a hard-coded fallback cascade (display_name -> username -> email) that isn't broadly applicable in my opinion. It's best left to the application to decide how to handle empty fields.
• zfcUserLoginWidget should be offered as an addon module for those who need it

[adamlundrigan]

#554 will need an update if this is merged

[Danielss89]

Agree, let's drop those.

[stijnhau]

Indead the widget should be a separate module.

the zfcUserDisplayName is indead kinda lame because is 100% harcoded.
I see a use case for it but then the field to show should be configurable.
i think this is even better then removing it.
In that case we can use that simple helper to show the most important field of the user.