Resolve "Empty lines in the height file"
With this MR empty lines (whether at the end of the file or in between) are ignored in the height file and the markerID file.
The .3dc file did already manage to work with empty lines at the end of the file. It cannot manage empty lines in between, but I think that is acceptable.
If another file format we support has this problem, a new issue should be opened.
Closes #322 (closed)