Facederivatives

Fixing face derivative calculations for collapsed elements. The previous face calculations only worked for tricubic-Hermite elements. Some examples, e.g. linear Lagrange-bicubic Hermite, will change as things are now done correctly. Fixed exporting of sector elements. The code no longer crashes but it still doesn't produce .ex files that can be read into cmgui. 
The only way to get the same constant for both C and Fortran would be to have a file with #defines and then #include that file in the C and Fortran source. All this field IO code is on death row so there is a question about how much work is done on it.