Extend charset for Anytone

[majkrzak]

Intro

While experimenting with APRS and AT878UVII+ I've accidentally find out that it supports much more than just ASCII characters. Further play with their CPS and scrolling through the font file, made me believe that it is the GBK encoding.

Details

GBK encodes ASCII characters on one byte, and non ASCI ones on two bytes. This could explain why some 16 characters fields are 32 bytes padded.

QT supports GBK through QTextCodec. I've made my implementation on top of it and it seem to work as expected.

TL:DR

This PR should give us possibility to use fancy characters like: "∮" or "№ " (see). It will also let something like naming "hotspot" as "ホットスポット" :blush:

TODO:

• [x] Implement GBK encoding/decoding
• [ ] Implement GBK RadioLimit
• [x] Use GBK in channel name as POC
• [ ] Use GBK where it is supposed to be used
• [ ] Rewrite encoding/decoding (cleanup explicit for loop)
• [x] Fix yaml saving issue (qdmr fails to save the utf characters)
• [ ] Prepare graphic with Anytone font