param_help.py: pretty-print Bitmask in eg. 'param help GUID_OPTIONS' output

[peterbarker]

After:

param help GUID_OPTIONS
STABILIZE> GUID_OPTIONS: Guided mode options

Options that can be applied to change guided mode behaviour



Bitmask: 
	  0 : Allow Arming from Transmitter
	  2 : Ignore pilot yaw
	  3 : SetAttitudeTarget interprets Thrust As Thrust
	  4 : Do not stabilize PositionXY
	  5 : Do not stabilize VelocityXY
	  6 : Waypoint navigation used for position targets
	  7 : Allow weathervaning

Before:

STABILIZE> param help GUID_OPTIONS
STABILIZE> GUID_OPTIONS: Guided mode options

Options that can be applied to change guided mode behaviour


Bitmask : 0:Allow Arming from Transmitter,2:Ignore pilot yaw,3:SetAttitudeTarget interprets Thrust As Thrust,4:Do not stabilize PositionXY,5:Do not stabilize VelocityXY,6:Waypoint navigation used for position targets,7:Allow weathervaning