[suggestion] Optionally use "Contacts+" for integration with owncloud contacts

[ERamseth]

There is a more feature rich (although possibly less mature/tested) contacts app for owncloud called Contacts+. When I switched to it, rainloop-owncloud contacts integration broke (probably because the back-end integration is hardcoded to work with the official contacts app). I'm suggesting enabling the same sort of integration with the Contacts+ app.

Contacts+ can be found here: https://github.com/libasys/contactsplus

[farson2003]

Yes!

[DJCrashdummy]

@RainLoop this is obsolete (and should be closed) for quite a while now: https://github.com/libasys/calendarplus/issues/202#issuecomment-157280303