Missing element US3

the behavior also the same as user beam element, seems it does not yet supported by CGX.

**edited
may i corrected, finally i found it how to be working. thanks Guido for implement the improved version of classical shell element, also for some example files at the webs.

or, may also thanks to another. did Gil Rama at MTU Aero Engines (et al) contributed directly to CalculiX?