Rename APIv1Controller to APIv1UserController

All existing actions were user related.
New API v1 actions can now be placed on new, specific
controllers.
[API] Alias /prefs/friends to /api/v1/me/friends
/api/v1/me/friends: No need for backwards compat

/prefs/friends for API consumers includes an empty
list as well as the friends list, for JSON compatibility
with the old format. No need for that here, so apply a
minor shim to not have it.
[OAuth2] Add friendlier endpoints for friends

PUT /api/v1/me/friends/{name} to add a friend
GET /api/v1/me/friends/{name} to get info on that friend
DELETE /api/v1/me/friends/{name} to unfriend
Ratelimits: Ignore unavailable of ratelimitcaches
Ratelimit: Support setting higher limits by client