Better sanity checks in ConvertProjectToHDF.py

[schwancr]

We have the machinery set up to do this (validators), but I don't think the script actually uses any of it!

This would have prevented issue #309

[kyleabeauchamp]

I think this isn't too hard, but it does require us to preselect a reasonable distance or RMSD cutoff heuristic. The challenge here is that discarding data without justification (or warning) is an equally poor outcome.

[schwancr]

I think we can at least check for the really obvious things, like NaN's and infinities

[kyleabeauchamp]

Yeah, good point we can do that always.