Netgen 5.1, new Mesher: Netgen CSG
Merge branch 'master' into devel

Conflicts:
	examples/tutorial/CMakeLists.txt
added get required input for base parameter handles
added extract_filename and extract_path
added default mesh meta function
new file location, added generic function, more mesh types supported
using max size for finding identic surfaces
new location, new namespace, better implementation of VTK reading (support for pvd files, more meshes supported)
new file location, new namespace, more mesh types supported
added pugixml
some file changes, new namespaces (viennamesh::io), algorithm naming changes (file_reader/writer -> mesh_reader/writer)
Fixed implementation with multiple meshes (duplicate lines)
added support for line meshes
added conversion of segmented mesh to triangle mesh
added line coearsening, laplace_smooth and linear_transform algorithm
added new algorithms: laplace_smooth, line_coarsening, linear_transform
added (const_)parmaeter_set::set() overload for non-const char pointer strings
new examples
pre-move commit
example for reading a GTS deva file