adjusted interpolation method: points can be 20% instead of 10% outside of box to find a proper value

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!