https://gitlab.com/gitlab-org/gitlab-ce/blob/8-16-stable/doc/api/repositories.md - optional "ref_name" for V3
https://docs.gitlab.com/ce/api/repositories.html - optional "ref" for V4

* Complete the javadoc of NoteApi and LabelApi

* Fix createLabel and updateIssueNote

* [Add]Add gitlab project milestone api.

* [Add]Check projectId not null.

* [Fix]Fix some bugs.

* [Add]Add gitlab issue notes api.

* [Add]Add gitlab labels api.

* [Imp]Add attr-required to Param.

* [Fix]Fix test error.

* Get project users (not members)
https://docs.gitlab.com/ce/api/projects.html#get-project-users

* Removed wildcard imports