Now that the main partitioning refactor patch is merged, there is
a small relict of handling partitions still in the disk-image-create
main.
This patch moves the functionality from disk-image-create to the
block-device/partitioning module: it is mostly a rewrite of the
original bash code in python.
Change-Id: Ia73baeca74180a7bc9ea487da03ff56d6a3070ce
Signed-off-by: Andreas Florath <andreas@florath.net>