Add --factory in crosh update_firmware command and make default as --rw-ab-together
Add --factory in crosh update_firmware command and make default as --rw-ab-together

This is the last piece of issue 5244.
"update_firmware" command in crosh will update RW firmware section,
and --factory will invoke "factory" (RO+RW) update process.

BUG=chromium-os:5244
TEST=manually:
1. create a recovery image with firmware updates (you can get that
   from latest builds for dedicated platforms as Z* / M*),
   boot and ctrl-alt-T to enter crosh
2. type "help"
   Expected: found "update_firmware [--factory]" item
3. type "update_firmware --blah"
   Expected: return error as "Unsupported option: --blah"
4. type "update_firmware --factory"
   Expected: firmware updated including RO section.
   You should see some "factory" in response messages

Change-Id: Id569e63f8c070ccc92b41ef997fd42e9e06989cf

Review URL: http://codereview.chromium.org/3447013

joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager