Utilization check for roof battens, combination of forces in two directions

• moment check for My and Mz
• shear check for Vy and Vz

Links:

• https://github.com/Anthrazit68/NODEMaple
• https://www.moelven.com/globalassets/moelven-limtre/limtre_eksmpl_digital.pdf
• https://www.moelven.com/globalassets/moelven-limtre/limtreboka_2015_el2.pdf