New UI, localization, multichannel support and TPDF dithering for 16 bit

This is a major new release, see the changelog for more details.

A major change is the ability to select the sample rate in the Audio TAB, this may affect you on Linux.

Linux Appimages in assets, built on Ubuntu 20.04LTS, can be updated with AppImageUpdate.

Windows Setup, and debug/release binaries in assets.