replaced implementation of static Size template with generic constexpr function

src/amdis/common/Apply.hpp

src/amdis/common/ForEach.hpp

src/amdis/common/HybridSize.hpp

src/amdis/common/MultiTypeMatrix.hpp

src/amdis/common/MultiTypeVector.hpp

src/amdis/common/QuadMath.hpp

src/amdis/common/Range.hpp

src/amdis/common/StaticSize.hpp

src/amdis/gridfunctions/DiscreteFunction.inc.hpp

src/amdis/io/VTKWriter.hpp

src/amdis/localoperators/ConvectionDiffusionOperator.hpp

src/amdis/localoperators/FirstOrderDivTestvec.hpp

src/amdis/localoperators/FirstOrderGradTest.hpp

src/amdis/localoperators/FirstOrderPartialTest.hpp

src/amdis/localoperators/FirstOrderTestDivTrialvec.hpp

src/amdis/localoperators/FirstOrderTestGradTrial.hpp

src/amdis/localoperators/FirstOrderTestPartialTrial.hpp

src/amdis/localoperators/FirstOrderTestvecGradTrial.hpp

...amdis/localoperators/SecondOrderDivTestvecDivTrialvec.hpp

src/amdis/localoperators/SecondOrderGradTestGradTrial.hpp