Add framework for Spark Core board support.  The initial commit is a clone of the Maple Mini and still needs Spark customizations

Add freedom-kl25z/minnsh configuration:  This is an experiment to see just how small we and get an NSH configuration.  From Alan Carvalho de Assis.

KL25Z:  Add low-level up_lowgetc function that can be used to provide an NSH console when the file system (and hence the serial driver) is disabled.  From Alan Carvalho de Assis

The last checkin replaced some impossible error handling with DEBUGASSERT.  Except that one of the case is actually possible in one cornercase and had to be restored

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

SAMA5 OHCI:  Fix some problems with D-Cache coherency and physical addressing related to interrupt endpoints

SAMA5 OHCI:  When UPLL drives OHCI the logically correct divider of 10 does not work;  But a divider of 5 does.  Why?

A consequence of previous change:  Configurations that select a PHY also need to set CONFIG_NETDEVICES or PHY configuration will be lost on the next reconfiguration