Multiuser love for LocationManager

LocationManagerService now keeps track of the current user ID and
denies location requests made by all but the foreground user.

Additionally, location settings are now user-specific, rather than
global to the device. Location provider services now run as specific
users, and when the device's foreground user changes, we rebind to
appropriately-owned providers.

Bug: 6926385
Bug: 7247203
Change-Id: I346074959e96e52bcc77eeb188dffe322b690879