Add packet_id AUTO INCREMENT field to sensor_packet table
Add applyTri to attempt TRI on recent packets

The previous trilateration method (having trilateration trigger
on packet submission) is plagued with potential synchronization
problems, as it may ostensibly be called at the same time when multiple
sensors attempt to submit simultaneously.

The chosen alternative involves having a standalone script running
the applyTri method, which will loop continuously over the submitted
packets to find matches.  This solves the synchronization issues,
but opens several difficulties in packet triangulation.

The applyTri method is completed, but several helper functions it
relies on are as-of-yet unimplemented.  The function is untested as
no sample data is available
Strip trilateration from sensorsubmit.php

As trilateration no longer occurs immediately after sensorsubmit, the code
needed to be stripped out and put elsewhere.  The code removed from sensor
submit is added to trilateration.php in subsequent commit
Further refactor from sensorsubmit.php to trilateration.php