Manager/Admin changes User's position

[Zackeree]

MSS:

1. Manager/Admin views their Users(#35)
2. Manager/Admin selects User
3. Manager/Admin changes the User’s position

Extensions:

3a: User isn’t a subordinate of Manager
    .1: Notify Manager
    .2: Manager/Admin may continue (some Users can have multiple managers/overseers) if they have permission

Requirements:

• [ ] Manager/Admin searches for User (#35)
• [ ] Manager/Admin adds User as Subordinate
• [x] UserController method changePosition