CMakeLists: Check for parallel splash install

- CMake Errors are FATAL (and stop processing, not only generating)
- Splash: check for parallel support in splash.h
- Splash: switch hdf5 depencency to make it right
  (installed hdf5 does not require splash but vice versa does)
Outputs: Splash -> libSplash
Merge pull request #85 from ax3l/topic/CMakeSplashParallel

CMakeLists: Check for parallel splash install