Create and edit files in web editor via rugged

- [x] create file via rugged
- [x] update file via rugged
- [x] remove file via rugged
- [ ] fix tests
- [x] remove satellites code
- [x] create activity event for new/edit file via rugged
- [x] base64 support

Part of https://dev.gitlab.org/gitlab/gitlabhq/issues/2300

See merge request !751