vertex.pt integrated into vertex; *.pt replaced with vertex
renamed: hiPt -> vHigh, loPt -> vLow
some renamings for consistency
Trapezoider.js: inline documentation
update_trapezoids: integrated -> add_segment
Polygon Triangulation: u0/u1, d0/d1 -> uL/uR, dL/dR (part 1)
Polygon Triangulation: u0/u1, d0/d1 -> uL/uR, dL/dR (part 2: Tests), finished