Facility for cross-building RocksJava using Docker

Facility for cross-building RocksJava using Docker

Summary:
As an alternative to Vagrant, we can now also use Docker to cross-build RocksDB. The advantages are:

1. The Docker images are fixed; they include all the latest updates and build tools.
2. The Vagrant image, required scripts that ran for every build that would update CentOS and install the buildtools. This lead to slow repeatable builds, we don't need to do this with Docker as they are already in the provided images.

The Docker images I have used have their Docker build files here: https://github.com/evolvedbinary/docker-rocksjava and the images themselves are available from Docker hub: https://hub.docker.com/r/evolvedbinary/rocksjava/

I have added the following targets to the `Makefile`:
1. `rocksdbjavastaticreleasedocker` this uses Docker to perform the cross-builds. It is basically the Docker version of the existing Vagrant `rocksdbjavastaticrelease` target.
2. `rocksdbjavastaticpublishdocker` delegates to `rocksdbjavastaticreleasedocker` and then `rocksdbjavastaticpublishcentral` to upload the artiacts to Maven Central. Equivalent to the existing Vagrant target: `rocksdbjavastaticpublish`
Closes https://github.com/facebook/rocksdb/pull/2278

Differential Revision: D5048206

Pulled By: yiwu-arbug

fbshipit-source-id: 78fa96ef9d966fe09638ed01de282cd4e31961a9