refactoring, new interface paradigm

src/polymesh/EdgeHandle.hh

src/polymesh/EdgeIndex.hh

src/polymesh/FaceHandle.hh

src/polymesh/FaceIndex.hh

src/polymesh/HalfedgeHandle.hh

src/polymesh/HalfedgeIndex.hh

src/polymesh/Iterators.hh

src/polymesh/Mesh.hh

src/polymesh/Ranges.hh

src/polymesh/VertexHandle.hh

src/polymesh/VertexIndex.hh

src/polymesh/cursors.hh

src/polymesh/iterators.hh

src/polymesh/ranges.hh