GPS SIMULATOR EXIT ON PLAY FIX

Now, if you exit the GPS SIMULATOR while transmitting, it will properly stop the radio and won't crash, exiting as expected.

Antenna length Calculator fix

Calculation now rounds up decimals so result is more accurate.

Update README.md

Remove clunky text when changing to HackRF mode

Renamed scanner squelch to trigger
Added squelch for audio output

Scanner features (#55) - Added freq description to scanner display.