build a static cockroach binary

edit: latest update at the bottom.


* added a `make build_static`
* vendored in everything that was left: bz2, zlib, protobuf
* build only static libs
* light brushing up of the Dockerfile

next up: a small Cockroach deploy image, built after successful tests through CircleCI.
A comment up here would be worth a lot. Maybe something along the lines of this script using a cockroach development container to build statically linked binary and tests, exporting these to a local directory, and then building a minimal container using the dev-container-built statically linked binary and tests.