Refactor (split) trilateration.php

Trilateration.php became slightly bulky as it contained functions both for
the mathematics of a single trilateration as well as the policy of how
bulk trilateration is done.  These two semantic blocks were split into separate
files: trilateration.php containing the mathematics from a single trilateration,
 and triPoll.php involving the functions dictating the policy of bulk
trilateration polling.