fixed gmshinterface; fixed mesh copy constructor; fixed layer mapping; removed various TODO6 tags. DIRECT STs still not working; FEFLOW and TETGEN still not working; getsurface still not working

This reverts commit 05677165.

Conflicts:
	FileIO/XmlIO/XmlGspInterface.cpp
	README.md

- changed function scpr - for vectors of size 3 there is a specialisation of the function template which avoids OpenMP technique for very small vectors

renamed namespace GEOLIB to GeoLib in order to be consistent with other OGS-libraries and directory names

- renamed method to access coordinates from getData() to getCoords()

added test application for mesh reading, fixed some bugs, reading and creating a mesh is working now; Mesh is (for now) a friend of Node, this should be fixed soon.

changed size_t to unsigned; included a few (yet unimplemented) methods for mesh-consistency checking

put nearly the whole CG method working loop into #pragma omp parallel to avoid overhead for parallelization

try to improve speedup using other OpenMP pragmas, reducing the number of parameters of function scpr and omit a initialization of a vector

- applying changes to interfaces