Add "is root" attribute to users

[stopfstedt]

• root users can access everything at all times, instance-wide.
• check for root needs to be wired into all voters, the root-check will need to precede any other authorization checks within these voters; essentially short-circuiting those.
• exclusive capabilities of root users:
  • can create schools
  • can delete schools
  • can flag other users as "root"
• add 'isRoot' attribute to User entity
• create console commands for setting/un-setting the isRoot attribute on any given user
• ensure that only root users are able to modify the isRoot attribute on any given user via the API

[stopfstedt]

refs #1511

[stopfstedt]

make sure to bake an extra perms check into the user controller's POST and PUT action to ensure that the current user has rights to set/modify the 'root' flag.

[jrjohnson]

@stopfstedt - I think this can be closed, yes?

[stopfstedt]

the answer is YES.