mTECS

This is Thomas' total energy control system. Heavily tested in the last days, its now a good time to start ironing out the last kinks and establishing trust logs. Should also be made the default on master.

@thomasgubler @sjwilks @AndreasAntener Please provide additional comments here.  Less branches will mean less confusion in the next weeks testing 8).
This goes into the same directions as my comments here https://github.com/PX4/Firmware/pull/1036
--> Let's extend the interface when we need it