Raster to mesh conversion (#1991)

* reimplemented raster to mesh conversion

* fixed index issues and added 3d index calculation

* added necessary changes to gui dialogue

* added tests

* clang format

* added ifdef for data explorer/vtk includes

* modified dereferencing of unique pointers, formatting

* changed pointer to vector in vtk prep

* using const& for nodes vec

* fixed remaining occurences of dereferencing raster object