Morse decoding

[bjorgan]

See https://github.com/ag1le/morse-wip or https://github.com/magnemahre/morse-wip. This should be good enough, at least as a start. Must be made thread-safe, and probably be included as a separate library.

Need interface for recording decoded text, and control over which parts of the text have already been obtained and displayed on the GUI. Morse decoding thread should run by itself without intervention from the rest of the program until the signal has stopped, and continuously spew letters to a buffer? Should the number of morse decoding instances be limited to a predefined number, and then assign the instances to a new signal when it appears and de-assign instances when the signal stops? Connect decoded text to the signal bin, and not the decoder instance itself?