Now defaults to 16 on both frontend and backend.

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* Add a migrat service type switch page

* Improve translations

* remove images

* Fix images

* remove extra create repo button on dashboard

* Follow reviewers' opinions

* Fix frontend lint

* Remove wrong submit file

* Fix tests

* Adjust the size of image

* Apply suggestions from code review

Co-authored-by: 赵智超 <1012112796@qq.com>

* Remove username and password from migration of github/gitlab

* Improve docs

* Improve interface docs

Co-authored-by: 赵智超 <1012112796@qq.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>