## New `vtkBTSReader` for Engys' BTS (Binary Triangulated Surface) files

You can now read in .bts files generated by Engys' HELYX and ELEMENTS software.
Compared with .stl files, .bts files are smaller and faster to load.
The file type also supports multiple solids.

The output of the reader is a `vtkPartitionedDataSet` where each partition is a `vtkPolyData` representing one solid.
