Add Gerrit support

[petems]

There's a few customers using Gerrit, especially if they're using openstack, as it's what OS uses for codereview.

This should be the ticket to create the Key:
https://gerrit-review.googlesource.com/Documentation/rest-api-accounts.html#add-ssh-key

Not sure about the hooks

[abrader]

@petems Acknowledged. Gerritt supports both keys and webhooks in fact. Thanks for the heads up! I need to get the universal GMS Project_X module done, then implementing this and any other key/webhook facilitator will be way easier than in the past. I'll keep you posted.

[petems]

@abrader Cool, if I get some slack time I wouldn't mind giving this a go, I'll see if I can ping a methodology or something 👍