changed tetgen_cube to tetgen_simple (multiple meshes are tested), started with netgen_simple
Merge branch 'FlorianRudolf/feature-netgen-make-mesh' into FlorianRudolf/feature-tests
Merge branch 'FlorianRudolf/feature-parameter-interface-improvement' into FlorianRudolf/feature-netgen-make-mesh

Conflicts:
	include/viennamesh/core/algorithm.hpp
Merge branch 'FlorianRudolf/feature-netgen-make-mesh' into FlorianRudolf/feature-tests
added seed points to examples, added check_run for tests
cell_size is an optional parameter now, valid query required
Merge branch 'FlorianRudolf/feature-netgen-make-mesh' into FlorianRudolf/feature-tests
Merge branch 'FlorianRudolf/feature-tests' into next