Rework hack/ and build/ directories.

* Rewrite a bunch of the hack/ directory with modular reusable bash libraries.
* Have 'build/*' build on 'hack/*'.  The stuff in build now just runs hack/* in a docker container.
* Use a docker data container to enable faster incremental builds.
* Standardize output to _output/{local,dockerized}/bin/OS/ARCH/*.  This regularized placement makes cross compilation work.
* Move travis specific scripts under hack/travis

With new dockerized incremental builds, I can do a no-op `make quick-release` in ~30s.  This is a significant improvement.

hack/benchmark-go.sh

@@ -18,4 +18,6 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
-KUBE_COVER=" " KUBE_RACE=" " hack/test-go.sh "" -test.run="^X" -benchtime=1s -bench=. -benchmem
+KUBE_ROOT=$(dirname "${BASH_SOURCE}")/..
+
+KUBE_COVER=" " KUBE_RACE=" " "${KUBE_ROOT}/hack/test-go.sh" "" -test.run="^X" -benchtime=1s -bench=. -benchmem