added basic structure for creating subsurface geometries suitable for tetgen meshing
adjusted convertMeshToGeo to write a seperate surface for each matgroup
building a boundary mesh from rasters
moved LayerVolumes class and added removal of congruent triangles
integrated first version into GUI
added functionality to read and write TetGen smesh files
fixed index issue
added tetgen smesh conversion for 2D meshes
added epsilon for mesh to geo conversion
support for quad and removal of unused nodes
region attributes are now written to tetgen smesh file
region attributes are handled in volume generation
layer adding dialog writes smesh files now
added documentation
changes based on PR comments
added renamed LayeredVolume files
added constants and fixed smesh input index error
added data-dependent epsilon calculation
fixed index error occurring if line elements are present in original 2d mesh
fixed epsilon calculation and default raster value assignment