Currently a modal dialog is used directly in ImportGui.open()/ImportGui.insert() that makes it impossible to use the functions in a
script because they will be blocked
The static members of FemSetElementNodesObject are not defined in Fem but FemGui which the MSVC compiler doesn't like.
Furthermore it's a code smell to make them public and static and they are not even used by the class itself.
* Move global (non-static) variables into anonymous namespace to avoid possible linking issues that may cause UB
* Fix compiler warnings
* Do not reinvent the wheel and use boost::to_upper_copy instead of own implementation
