Add 'prioritize' command to cgpt tool.

This lets us reorder the priority of all the kernel partitions with a single
command, instead of a bunch of complicated and error-prone shell script
logic.

Change-Id: I21d39763ec5a748488d5319a987bcfe7c34ce4d0

BUG=chromium-os:9167
TEST=manual

In the chroot, do this:

cd ~/trunk/src/platform/vboot_reference
make
make runtests
make clean

Everything should pass.

Review URL: http://codereview.chromium.org/5352005
12 files changed