moved functions getFileNameFromPath(), getSuffixFromPath(), copyPathToFileName() and extractPath() from files StringTools.{cpp,h} to files FileTools.{cpp,h}

moved functions trim(), replaceString(), splitString() and template functions number2str() and str2number() into namespace BaseLib

This should fix #20.

OGS_VERSION_AND_PERSONS => x.x.x (author names)
OGS_VERSION             => x.x.x

changed error messages in meshlayermapper; adapted node numbering for geolib::surface and gmsh-import to be consistent with vtk & meshlib

removed unused experimental code for TetGen file output

getSurfaceMesh is working now; getSurfaceNodes is working now; meshes are now tested for unused nodes (such nodes are removed upon loading)

added check if nodes belong to any elements; reworked legacy mesh input to use getline command so that linux coding will hopefully be no longer a problem

added rapidxml method for reading vtu files; fixed problem in Mesh::setNeighborInformationForElements - EDGE elements don't have neighbors anymore because they also dont have faces

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