Moving tests to extra package again.

Reason: third party implementations of PDB (like in existing one in Scala or Clojure) also need to execute the same test suite.
Removing IDEA project specific settings.
Major change in build: switching from maven/tycho to maven-bundle-plugin.

This change guarantees to use the same (e.g. maven) build configuration on command line and in different ideas (i.e. Eclipse, IntelliJ IDEA).
One of the implications is, that dependencies are now resolved via maven and not anymore over MANIFEST.MF referenced p2 / OSGi component repositories.

It still has to be monitored if this build setting setup behaves (experimental).
Adopted Eclipse project settings. Make use of maven/m2e plugin.