def.h add config for Flexbot Nano boards

These were part of the quad and hexcopter kickstarter:
https://www.kickstarter.com/projects/1387330585/hex-a-copter-that-anyone-can-fly

They will be sold by http://flexbot.cc/ later this year.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
config.h: set options for Flexbot Nano Hex

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
MultiWii.h: add prototypes for go_{dis}arm()

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>