Preemptively added two new squawk datatypes

0x12: Server respond, don't require challenge
0x14: Sensor deny server challenge

These are purely tentative, and will remain so until they have been
okayed
Added peck payload tests
Added squawk path to nesting test
Separated payload unit tests into suites

Before, all payload tests were lumped into one huge suite. Now, they're
separated into their own suites.
Added check, so originIP != destIP
Added chirp unit tests
Added exit codes to payload tests

This will make the tests more flexible when testing unexpected input or
early termination
Split payload unit tests into separate files

There needed to be better organization in the payload tests. I've been
working on making them better organized.
Removed tentative addition to squawk

Tentatively added sensor denies server response. Until it can be
discussed, I've commented it out.