FreeNAS Code

Three quick changes:
o Move to creating 2 partitions to ping-pong between.
o Bump flash size to 1g (10^9 bytes, more or less).
o Implement generic flash sizes in nanobsd now that the bulk of the need to
have the geometry right is much less critical than it was in days of yore.

This should give us the necessary infrastructure to do upgrades form the GUI.