add Tests/NumLib in CMake
add a test for ShapeQuad4
add a shape function class for quad4
Add NumLib to doxygen inputs.
[NL] ShapeQuad4 correct argument names.
[NL] ShapeQuad4. Small numerical improvements removing for-loop.
[NL] Improve Doxygen output.
Merge pull request #218 from norihiro-w/feature-ASSERT_ARRAY_EQ-macro

Use ASSERT_ARRAY_NEAR macro
Merge pull request #216 from endJunction/Quad4ShapeFunctions

Quad4 shape functions
Fix merge error.
Merge pull request #222 from TomFischer/BugFixMaster

Fix merge error.
add FindEigen.cmake
add FemEnums.h having ShapeFieldType
add a struct ShapeData storing shape function matrices
add computeNaturalCoordinatesMappingMatrices()
include Eigen in Tests if OGS_USE_EIGEN
add a test for ShapeData
add tests for coordinates mapping