add global ConstVector, clean math::Vector

- add math::Vector which support const definition at compiletime on host and device
- clean math::Vector that implicit type conversion is not allowed
- fix all imlizit casts
- DataSpace inherit now direct from math:Vector<int,DIM>
- add new CONST_VECTOR with size iof a cell (float values) to gridConfig.unitless
change *.h guard to #pragma once
add comments, prepare pull request notes
Add libSplash Version Checker

- read patch level, too
- check for minimum version of libSplash, else ignore as if
  it would be not provided (missing plugins shall not throw
  errors)
Merge pull request #151 from ax3l/topic-CMakeSplashVersion

Add libSplash Version Checker
fix typo
Merge pull request #147 from psychocoderHPC/topic-ConstVector

const vector and vector refactoring