Unit Test: Added Semantic Version Test (Current version agains v2.1.5)

TestVersionSemantics adds testing of semantic versioning
of 2.1.5 gluegen-rt.jar against the current version within a unit test.

Currently we expect BACKWARD_COMPATIBLE_USER
and need to toggle this to NON_BACKWARD_COMPATIBLE,
if actually perfoming non compatible major or minor version changes.

The latter is allowed right now, since we increment from 2.1 -> 2.2!

- Added https://github.com/jeluard/semantic-versioning semver.jar (Apache License Version 2.0)