[WIP] Adding parallel testing ANT build configuration and related files

This PR tries to introduce parallel testing in our travis-ci tests.

As of my current experiments, this was the time for builds before parallel testing:

https://travis-ci.org/zendframework/zf2/builds/4627221 (basically between 6.5 and 9 minutes)

This is the time for builds AFTER parallel testing through ANT has been introduced:

https://travis-ci.org/Ocramius/zf2/builds/4632333 (between 3 and 4 minutes)

Now it really drills down to making this prettier and safer, so please ask me anything and I shall research.