initial firmware commit

no "read to run" version
further firmware
some further firmware work

+ RF working
+ bluetooth basically working

TODO:
- switch on / off
- ...
bluetooth pairing possible
sleep basically works; basic RF transceiving works
layout & schematic fixes

+ layout: better ground flow
+ layout: more space for single parts
+ layout: marked GND on battery
+ layout: marked pinouts
+ schematics: fixed USB-connect->USB-plus connection
prepared firmware for flashing via USB
firmware cleanups and TODOs, USB bootloader added

+ added 2 projects from Code Red Technologies to support USB bootloading