We never add things `into` projects, we just add them `to` projects. So how about we rename this to `add_users_to_project`.

Rename `projects_ids` to `project_ids` by following the convention of rails.

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

I opted for admins to be added as "owners" instead of "masters" because project masters can managers members, but only group owners can manage members.

Rename add_users_to_project_teams to gitlab:import:all_users_to_all_projects