Add GitLab API backend for groups -> orgs endpoint

Add GitLab API backend for groups -> orgs endpoint

See https://gitlab.com/gitlab-org/gitter/webapp/issues/1445

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This endpoint will now return your GitLab groups if you are signed in with GitLab,

GET http://localhost:5000/api/v1/user/:userId/orgs

Testing strategy

1. Try the API with a GitLab user GET http://localhost:5000/api/v1/user/me/orgs
2. Try the API with a GitHub user
   1. GET http://localhost:5000/api/v1/user/me/orgs
   2. Community creation flow and open up the "GitHub projects" area from the first step

Dev notes

• https://docs.gitlab.com/ee/api/groups.html
• https://developer.github.com/v3/orgs/
• https://www.npmjs.com/package/gitlab
  • 3.6.0: https://github.com/jdalrymple/node-gitlab/tree/2ee7f113364e6824942f10c8d967d8e662a3cdc2