added new comparison operator to D3vector. Fixed bug in direct interpoaltor : didnt work, if the gridsize was non constant in all blocks. Also added Markers to mark surfaces properly.

Neue funktion Calculate_boundary hinzugefügt, welche einen Marker übernimmt. so kann angegeben werden, für welchen rand die LSM berechnet werden soll.

added the direct interpolator class. Now it is possible to interpolate in the unstructured grid directly, without crating an intermediate mesh. slow for random access, but for structures access (as in ray tracing for example) similar to the intermediate method. Benefit: more accurate!

face transform now working FINE ! Implementation is not perfect though, but since this is only called once, shouldn't make a big difference in performoance.

face transform almost finished. missing is only the correct implementation of edge transform, in case face transform is present.

bug in curved surfaces of ug_lens fixed, now resembles a sphere. next step is fixing the inner transfomrations.

working on transformation of faces: transform_inner_faces_NE_quad working, next step ,not yet done, is transform_diag_inner_faces_NE_quad