IMU.cpp: Altitude hold fix by Happul3

See http://www.multiwii.com/forum/viewtopic.php?f=8&t=4992&start=10#p49929

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
GPS: start parsing on 2D fix instead of waiting on 3D fix

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>
Add Flexbot serial-over-bluetooth protocol

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
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>
EEPROM: add flexbot default modes

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
EEPROM: only activate baro mode in aux2 mode

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
def.h: add battery scale for flexbot nano

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
HACK: log battery voltage ADC reading as debug[1]

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
HACK: decrease default rate/expo

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

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
MultiWii.cpp: add more parens to failsafe logic

See issue #17

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
config.h: enable failsafe

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