DUNE/Control: Added functions to set each gain in DiscretePID.
Control/AUV/Attitude: Roll gain may now vary with forward speed.
Config: auv/control: Added default configuration for roll compensation.
Control/AUV/Attitude: Roll compensation now encompasses offset compensation as well.
Config: auv/control: Added configuration parameters for roll offset compensation.
Merge branch 'master' into feature/roll_compensation
Control/AUV/Attitude: Using minimum and maximum value for roll gain. Specified units for speed bounds.
DUNE/Control: Minor comment cleanup.
Control/AUV/Attitude: Minor comment cleanup.
Merge branch 'feature/roll_compensation'

Feature #3187: Roll's proportional gain may now change according to the
AUV's surge speed. Speeds bounds and minimum gain must be specified. Gain
will only change when the speed varies between the given bounds. The new
mechanism 'Roll Compensation' now encompasses offset and speed
compensation.

Authored by: Pedro Calado
Reviewed by: José Braga

This commit fixes #3187.