Align partitions on optimized boundaries

Since more and more drives are coming with 4K sectors, a 0 starting position
results in unaligned drives.

We could start the partition at a 4K boundary, but that still makes parted
whine because of alignment rules having to do with flash devices.  If we
start at 1M, all drives types are properly aligned, parted doesn't complain,
and we lose a reasonably insignificant amount of disk space.

So that's what we'll do.

closes #136