Smart Warnings for codeplugs

[infamy]

There are a few gotchas with the DM32 codeplugs that the user has to be careful of.

1. Channels need to be in zones or they are useless.
2. DMR Radio ID has to be set for digital channels
   ...

Let's get a decent list of them and then we can either enforce them and/or at least warn if a user is going to write a codeplug with an issue.

[infamy]

Partly implemented in #107

[infamy]

Added code to warn if a dmr radio id in a channel is set to a dmr radio id that is missing. Should most likely set this to the last value, or first value in the dmr radio list. As this will cause a null channel error.

[infamy]

Closing this for now unless other ideas come to mind, in which case a new issue will be created.