Extend stack debug logic to include IDLE and interrupt stacks.  Also color the heap as well.  Based on suggestions from David Sidrane

Add interface definition for platform-specific storage of configuration data; Modify NxWM unit test to use these interfaces, if available, to save and restore touchscreen calibration data.

Telnetd:  Missing argument in debug statement can cause crash in certain error conditions.  From David Sidrane

New touchscreen scaling algorithm for the case where measured X values vary with y position (and vice versa)

NxWM::CCalibration: Add logic to collect and average samples, optionally discarding the most extreem values

Misc changes to README files; Update SAMA5D3x-EK NxWM configuration to use Calibration instruction messages

NxWM::CCalibration:  Add an option to provide some instructions in the center of the calibration screen

apps/system/sysinfo:  Ken Petit reportst that the sysinfo command's stack size is marginal.  Stack size is now configurable with a default of 1024 bytes