Hardware compatibility update uses standard (non-realtime) kernel

This release addresses USB problems seen on newer Raspberry Pi hardware versions including 8GB. No new functionality since v1.1.0 release, but uses standard kernel instead of realtime kernel. Jamulus runs fine under either kernel, so this mainly impacts what else your Raspberry Pi can do while running Jamulus. For example, if you drag a window around while running Jamulus on standard kernel, you can hear some audio degradation due to increased jitter. Keeping this in branch jambox-8gb for now, Minor changes to README.md in that branch to reflect ALSA device numbering changes under standard kernel.

A pre-built image file is available:
https://jambox-project.s3-us-west-2.amazonaws.com/releases/image_2020-12-09-Jambox_pi-gen_v1.1.1-8gb.zip