Previously, clientside representations of players were able to move to a new exterior cell once during their movement tick and then again when sending a cell change packet to the server. Besides causing crashes in CellRef because of a messy cell-changing record, this also led to major desyncs.
Clientside representations of players can now only change their cells when a server-sent cell change packet specifically allows it.
Make the local player send a packet whenever moving from one exterior cell to another, don't require objects to have RefNums to be moved correctly between exterior cells, and increase the packet priority for cell changes.
