Functionality of make_watertight

[makeclean]

Determine the proper functioning of make_watertight on models that are water tight and those that are not water tight.

[makeclean]

make_watertight should not further damage already water tight models, it should however have a beneficial action upon non watertight models. Currently on a non-watertight model the code does nothing, it performs various "fixing" actions but does not write these changes to file. In both our stand alone version and the meshkit version.

[makeclean]

Given the fixes to remove the segfault problems 513b71c, we can now focus investigation to issues as to why the models are not modified when the model is not watertight.

[makeclean]

Test case 1, faceting tolerance 1.0e-2, produces the facet file shown in red, introducing a 0.1 deviation in the z coordinate of the last vertex produces the green.

Zooming into the offset region,

The desired behavior is that check_watertight determines that the model is not watertight at this tolerance, and then make_watertight should fix that vertex.

faceting tol	1.0e-1	1.0e-2	1.0e-3
check_watertight	watertight	not watertight	not_watertight
make_watertight	no changes	no changes	no changes

So the correct behavior would be to make no changes to the model for a faceting tolerance of 1.0e-1, but to fix the changes for other faceting tolerances.

[makeclean]

In case it wasn't clear, a faceting tolerance of 1.0 causes many things to break down, originating from weird faceting from CGM.