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

apps/Makefile should include external/Make.defs so that external applications can participate in the menu configuration

Another case where we should use the routing table: There may be multiple routers on the same network.  In that case, we have to search for the routing table for the router that forwards to the destination address.  We do this when we determine the MAC address we want in the ARP logic

More improvements to the minimal NSH when there is no file system and when print fieldwidths are suppressed

Mov apps/examples/composite to apps/system/composite; convert configs/stm3210e-eval/composite to use kconfig-frontend tools -- untested

Fix warnings in USB MSC when compiled for a high speed device; also fix USB MSC default VID/PID configuration

Suppress attempts to manage USB trace if the USB MSC example is built as an NSH built-in application.  In that case, USB MSC does not do a good job managing trace data and gets in the way of other things that can do a better job (like NSH or the USB monitor).

DHCPD: Fix calculation of lease address.  Bad logic causes repeated assignment of the same IP address.  SourceForge bug #21 from Paolo Messina.