added functionality to find all nodes that are connected via edges and via element to other nodes; replaces all cout's with appropriate logog messages

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

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()

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

added some basic functionality (get, add, etc.) and introduced an example finite element class for tetrahedra