Merge pull request #642 from RocketChat/custom-oauth

packages/rocketchat-custom-oauth/package.js

packages/rocketchat-gitlab/common.coffee

packages/rocketchat-gitlab/gitlab-login-button.css

packages/rocketchat-gitlab/package.js

packages/rocketchat-lib/package.js

...ges/rocketchat-lib/settings/server/addOAuthService.coffee

packages/rocketchat-lib/settings/server/startup.coffee

...ages/rocketchat-lib/settings/server/updateServices.coffee

server/configuration/accounts_meld.coffee

server/lib/accounts.coffee

server/startup/migrations/v18.coffee