Can save off logs with RNAV message, but not getting the right numbers
RNAV log messages added

Details about RNAV messages are outlined in RNAV_LogStructure.txt
Able to receive LED_bitmask over serial and added to RNAV log messages

Still need to use the result of LED_bitmask to know whether we can use
the new information received over serial or not.
Implemented ZOH when one or more LEDs fall out of frame

Should probably command level flight after a certain period of missing
data
Added handling of lost localization updates by commanding level flight
Increased rNav timeout to 5 seconds