Resolve "Logical error in Boundarygeometry"

• Closes #656 (closed)
• fix -Wrange-loop-analysis warnings like:

src/Classic/AbsBeamline/ElementBase.cpp:422:42: warning: 
      loop variable 'path' of type 'const std::vector<unsigned int>' creates a copy from type
      'const std::vector<unsigned int>' [-Wrange-loop-analysis]
    for (const std::vector<unsigned int> path: paths) {
                                         ^
src/Classic/AbsBeamline/ElementBase.cpp:422:10: note: use
      reference type 'const std::vector<unsigned int> &' to prevent copying
    for (const std::vector<unsigned int> path: paths) {
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                         &