Augmented UsrPorts option, as suggested by Glen Barber.

While I'm adding stuff to config.sh.sample, update a bunch
of the comments.
BeagleBone, RPi, PandaBoard and Wandboard are all armv6
Merge branch 'master' of git://github.com/kientzle/crochet-freebsd into arm-rpi-target-arch
Disable forceful '-j1'.

Sponsored by:	The FreeBSD Foundation