Cosmetic updates

ArduCopter Alt Hold - Change to not run get_nav_throttle if manually adjusting altitude with manual_boost - removes possibility of I term running up
Tuning - added ability to modify altitude (position, not rate) controller
TradHeli - Fairly large change to how throttle is scaled and collective moves.

made loiter radius smaller in storage

this sets pin 23 on the 2560 according to whether the USB cable is
connected or not

this allows it to build on linux/macos

this happened with an empty dataflash

fix ac2 heli error
fix guide mode wp
fix tuning graph on mono
fix autozoom on planner map
modify prefetch - current screen
fix zoom bar for mono
fix base class for special functions

shortened strings, logging defines updated