This introduces a way to upload prebuilts from the command line.
The following features are available
* Multiprocess upload (cuts time down by a 1/5th for uploading)
* Versioned uploading with git file commital
* Host prebuilt uploading
* Board prebuilt uploading
BUG=chromium-os:4843,chromium-os:5855
TEST=./prebuilt_unittest.py
{'/b/cbuild/build/chroot/build/x86-dogfood/packages/x11-misc/util-macros-1.5.0.tbz2':
'gs://chromeos-prebuilt/host/version/packages/x11-misc/util-macros-1.5.0.tbz2',
'/b/cbuild/build/chroot/build/x86-dogf}
.FILTERING /usr/local/package/oob
FILTERING /var/tmp/bibby.file
.....Updating stage 20100309/stage3-amd64-20100309.tar.bz2 to stage
test_update
.
----------------------------------------------------------------------
Ran 7 tests in 0.002s
OK
