Instead of re-uploading the mesh each time the range changes, handle the range in the shaders with the new draw-range parameters. This does however, mean the range has to be in vertices, not in elements. This necessitates some changes to the simulation-view, and some added bits deeper in the base code. Mainly, since each time the type of a line changes, there is an extra vertex, there needs to be a type-change count available to get from 'paths' to range indices.
Changed to "is None" insted of "== None" to test if numpy.array was initialized
Added extruder to PathSegment in Cura.proto
Changed index_pattern to class variable in Layer.py
