R1:6b1b21c999da

Move member/watch actions to "Members/Watchers" page

Summary:
Ref T10054. This tries to make the members page a bit more consistent and provide hints to users about subproject/milestone membership rules. In particular:

- You now join, leave, watch, unwatch, add and remove members, and lock and unlock membership from the members screen.
- We now explain the membership rule for the project on this screen. There are currently four rules:
- Normal Project: Join/leave normally.
- Parent Project…