Partly fixing #76 and #80 - Example file not working

[christophKaiser]

While loading vertical-alignment.ifc and linear-placement.ifc, I got the following error, which was probably meant as 'crash' in #76 and #80 by @SamuilsRulovs:

After change the arguments of IFCSIUNIT from $ to * (according to commit 'Corrected all IFCSIUNIT-s in all files.') the error doesn't appear anymore.

However, the vertical alignment doesn't look correct in the viewport (kink / jump at the right side of the picture): The linear placement loads, as well - but it takes quite long. However, I haven't had time to investigate the result in more detail.

Thus, both issues probably wouldn't be fixed completly with this small change - but it will improve the current situation at least a bit.

I came over that because I had the similar error message (but with different background reason) in my current issues about IfcBSplineSurfaceWithKnots, respectively basin-advanced-brep.ifc.

[pjanck]

As for the other comments:

• every file with a terrain model takes long - string parsing of the TIN is really slow (see #94 )
• the vertical calculation is somehow wrong (but only at the end of the alignment - known rpoblem, at least to me)