[OE-core] locking down patchwork and wiki registrations

[Khem Raj]

Hi

We receive tonne of spam in form of registrations everyday and some of
bots have become smarted that they even activate their
profiles. It has to be manually deleted and its tedious. I would
therefore like to remove the 'register' link from pw front page
that will stop the spam as I have already experimented with it a bit.

Same is also true for wiki. We should make the registration process to
be manual since that will put some end to registration spam.

I am open to other ideas to stop spam without locking registrations.

The registrations will still happen but should be done manually.

Thanks
-Khem