Allow coarse location check-in

[LGro]

Add toggle to truncate or randomly offset current location to obfuscate precise location when a user chooses to during check-in location sharing.

Alternatively, allow specifying a range of precision, say 500m, and then randomize the location point by that range, and also send the range in the location details, so that contacts can see a precision range circle at the precision distance for that person.