Improve building Java projects from source

[maltesander]

The PR #494 builds the HBase docker image from source.

Currently there are some fixes in place that are improvable.

Mainly:

1. The conf.py now has a version for java-base and java which currently both point to version 11. The java-base can not be used as variable in the docker image because docker will complain. Therefore the duplication.
2. HBase and Hadoop both are build from source, we could unify this into a java-dev image containing maven, git, gcc and all dependencies required to build java products from source.

We suggest to declare a JAVA_VERSION variable in the java-base image that can be used in images based on the java-base and/or java-dev image to get rid of the java version duplication.

Please have a look at @razvan comments in the PR, especially:

• Add Hbase new version 2.4.17 and compression #494 (comment)

[maltesander]

We added a java-devel image for builders and java-base for main images.