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. 
There are some tabs here and in a few other places in this file that mess up the indentation in my editor.