Envelope Member Diagrams, End-Release Visualization, Shear Wall Validation & Bug Fixes

• Added enveloping to member diagrams. Set combo_name to a list of combo tags and the member diagram will show an envelope of all the combos that have any of those tags.
• Bug fix: Quadrilateral element displacements had corners swapped during VTK visualization. This was a relic from the old MITC4 formulation that has been corrected.
• Bug fix: Added shear wall and mat foundation load cases to FEModel3D.load_cases(). The list of load cases was sometimes incomplete if these meshes had not yet been generated.
• Added bending moment end releases to visualizations.
• Bug fix for shear walls with flanges having an origin with their origin at Y != 0.
• Rectangular meshes now filter out user defined control points that erroneously lie outside their boudaries.