Removes the old fake input on the Codebase migration screen, and adds the disable_form_autofill
* Migrating wiki don't require token, so we should move it out of the require form * Fix lint
This PR adds [GitBucket](https://gitbucket.github.io/) as migration source. Supported: - Milestones - Issues - Pull Requests - Comments - Reviews - Labels There is no public usable instance so no integration tests added.
