Minor cleanups

Awesome work - that did not looks as straight forward as we thought.

### Proposed improvements:

- you seem to [<3](https://github.com/ComputationalRadiationPhysics/libSplash/commit/8a3fc166827d1fec708a66a3244db1518fd2bf39#L0R44) warnings a lot, so I added `-Wextra` >:) *evil*
- I was so kind to mark all unused-parameters, they guys in [ParallelDataCollector.hpp](https://github.com/ax3l/libSplash/commit/885a6cc02029fa8008cb8dbbd8d6ddd1b62545ff#L2R417) confused me a little - they are all non-implemented but don't throw exceptions...?
- examples `#include "splash.h"` now, too
- the PostInstall script works in a [platform independet](https://github.com/ax3l/libSplash/commit/67a8b38518c155b38613cc4d5e74343da4e865ca) way now *hopefully*
- I added some missing newlines at EOF here and there

Cheers