Remove obsoleted CONFIG_SYSTEM_POWEROFF from configurations.  The NSH shutdown command should be available instead

Enable CONFIG_BOARD_POWEROFF=y.  Now you can use the NSH shutdown command to terminate the NSH session

NTOSD: Update and fix a configuration.  The way it was trying to disable the console and file system caused build problems

Fix references to the no-longer-existent misc/ directory in comments, README files, and documentation