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

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

Networking:  Fix backward conditional in test to see if address is in ARP table.  From Max Holtzberg

SAMA5 GMAC:  Initial driver check-in is just the EMAC driver forced to compile with the GMAC register definitions

SAMA5 EMAC:  Need to pace RX and TX because and RX can result in a TX; Process TX interrupt events before TX interrupt events for the same reason

SAMA5 EMAC: Add some need D-Cache Flush/Invalidate operations.  Add support for CONFIG_NET_DUMPPACKET

Move CONFIG_NET_DUMPPACKET from LPC17 and STM32 to commong network drivers.  Automatically enabled CONFIG_NETDEVICES when any Ethernet driver is enabled