Add a docker build file for building Accumulo and running test

I created the following little project. It helps someone completely new to Accumulo get to the point of building Accumulo and running the test really fast. I think it would be nice to include this with Accumulo under contrib/docker-build and then Accumulo's documentation could reference it.

https://github.com/keith-turner/accumulo-docker-build

Including it with the source has the benefit that it can be specialized for only the version it goes with. For example in the Accumulo 2.1 branch the docker build file in contrib/docker-build would only build Accumulo 2.1, it would not need to know how to build 1.10 or 2.2.

I cobbled this project together from Hadoop's Docker build and the existing Accumulo docker build files for running Accumulo. I need to quickly build a snapshot version of Hadoop once and their docker build made this super quick and simple for me.

Start with the linked accumulo-docker-build project and the existing Docker build files referenced in the issue, then review the contrib/docker-build location and relevant documentation. Done means the Docker build file is included for the applicable Accumulo version, builds Accumulo, runs its tests, and can be referenced by the documentation.

Written by the indexing model from the issue text.