housecleaning: delete everything thats dead or dying

- old build system goes away completely
- apps folder goes away completely - everything related to: freertos, echronos,
hwf4, stm32 booting code, is obsoleted by the tower9 build system and new bsp.
- ardupilot code is finally dead and gone! jamey's new ins has finally killed it
off.

And there was much rejoicing.