1) I corrected a couple of bugs in the XRay Image query that sometimes
   resulted in artifacts in the output images. The first bug was to
   reduce an epsilon in the intersect line with triangle code so that it
   wouldn't reject small triangles. The second was to change the intersect
   line with quadrilateral code to call the intersect line with triangle
   code twice, to avoid a problem it had with lines being nearly parallel
   to non-planar quadrilaterals. This resolves #1213.

   I also added the ability to create a vtk file of all of the cells that
   intersect a specific ray. This currently must be enabled in the code,
   but I will enhance it so that it can be done at run time for 2.7.

2) I made some corrections to the INSTALL_NOTES.



git-svn-id: http://visit.ilight.com/svn/visit/trunk/src@19769 18c085ea-50e0-402c-830e-de6fd14e8384