Experienced a problem where a user whose email changed was no longer
able to login. By using the ID as a primary identifier, we can avoid
conflicts of this variety within the github OAuth provider.
How it is solved:
* Take organizations_url field data from user basic data response
* Make another request to get all organization the user is a member of (public membership)
* Authenticate user if appropriate organization found in that list
* break out go and js build commands
* support oauth providers that return errors via redirect
* remove extra call to get grafana.net org membership
* removed GitHub specifics from generic OAuth
* readded ability to name generic source
* revert to a backward-compatible state, refactor and clean up
* streamline oauth user creation, make generic oauth support more generic
