OGM-316

Some improvements to speed up the build a bit:

* JavaDocs are not generated during build of OGM modules (there is a separate module for this)
* Only creating test JARs for those modules requiring it
* Skipping unzipping of AS if _-DskipTests=true_ is specified

In addition I've made the _hibernate-ogm-documentation_ module part of the default build. Obviously this increases build time but IMO it's a good practice to build everything by default (`mvn clean install`) to be sure nothing is broken and make things skippable on demand. The doc build can be skipped like this:

    mvn clean install -s settings-example.xml -DskipDocumentationBuild=true

This gives a good build time e.g. on dev machines, why CI would build everything (the motivation being that I recently caused a failure in the doc module which I didn't notice since its build was disabled by default).