setCrossSection method made virtual (needed by tr_shell01 element)
Improvements to support arbitrary component numbering in vtkxmlexportmodule
Fixing several issues in tr_shell01: supported set syntax for crosssections/material, fixing postInitialize issues
Updated oofemlib.cpp. Removed setMaterial (unused, should use cross-section instead).
Fixed so that "advanceSolution" can be called multiple times for the same time-step.