Read codeplug from radio into .rdt format

[d235j]

This would allow editing a codeplug already on a radio with available tools (which can be used in WINE), then writing the edited codeplug back using md380-dfu.

[travisgoodspeed]

This will let us program the radio with Wine on Linux and no Windows VM. High priority, much enthusiasm!

[ghost]

For reference, previous related issues in order of helpfulness for this: #41, #26, #2, #83