Document images.
Move ObjectDiff into util
Move Codec functions to their own file
Merge pull request #1690 from erictune/image_docs

Document images.
Merge pull request #1693 from smarterclayton/move_diff

Minor moves of functions into their own files
Use binary releases for cluster push scripts.

This is for GCE right now.  Other clouds/clusters are probably broken.
Tweak salt docs a little
Vagrant now using pre-built binaries.
Fix up kubecfg.sh script to find correct binary.
Remove unused manifest file
GCS uploads as part of release are now marked public and non-cached by default.
Normalize some of the boilerplate in each of the `build` commands.
Update build/README.md
Clean up READMEs and broken stuff.

Move all support for clouds that are broken with this change into an `icebox` directory.  We'll move that stuff back out as we fix it up.
Standardize how we refer to the kubernetes root.

Now use $KUBE_ROOT as the variable pretty much everywhere.
Set shell options for reliability.

Tweak a few other small things in our shell scripts.
Confirm pull of golang:cross as it is huge (1.8G)
Option in `build/release.sh` to skip tests for a quicker dev/test cycle.
Add a `release` target to `Makefile`

The rest of the reconciliation with new `build` methods will come later.
Apply SELinux policy to _output dir so "build in docker" works on RHEL.