Minor refactoring for cross compilation code.

1. Instead of using cross*/tools* in the project names, we simply place the
   project.cmake files under cross or tools subdirs (similar to what we do for
   all OSes.
2. Added ability to specify "CROSS_BUILD_SITE" specific defaults using
   ParaViewDefaults.${cross_build_site}.cmake file.
3. Removed ParaView/VTK/Protobuf patches since all those changes have now made
   it into the corresponding repositories.
4. Added cross-compilation defaults for Shaheen@KAUST.
Update URLs to point to paraview.org.

Change-Id: I798dc867440fe9f53420fa6432f52e5739ead332