PicoC: First running version for quanton and flyingf4

This is a port of the famous PicoC-interpreter. It uses an optional
stdIO console over USART and/or telemetry tunnel.
Temporarly removed the missing sensors from the FF4 target in order to
make the naked DiscoveryF4 bootable. This also adds some missing
HoTT-stuff to the FF4.