Improve gitlab integration when number of projects is large and groups are in use.
Rather than just fetch all projects and hope your project turns up in the first 100, if a group is specified, fetch the group list, then fetch its contents and scan for the matching project.
This also includes a bug fix, fixing issue where the POST body was not being passed through in the auth request. Would be surprised if this didn't also affect github integration.

Tested against one large gitlab installation over https, in development environment.
Also works well in production build.