Add Draft Bezier Curve draw & edit mockup using bSpline tools.
Draft Bezier Curves: Add functionality to mockup
     - Split poles to multiple bezier segments
     - set degree of bezier curve
     - Close Draft bezier curves
     - set Degree at creation
     - implement addPoint for piecewise Bezier curves

Draft BezCurve bugfixes
    - fix Close button for BexCurve Edit
    - fix tracker behaviour in for BezCurve.undoLast

Draft Bezier Curve: use circle trackers for control points

Draft: prepare functions to make bezier knots tangent or symmetric
Add BezCurve tangent/symmetric buttons to Draft.Edit
Draft: added functions to edit tangent or symmetric bezier curves
       changed icon Draft_BezTanNode
       bugfix in Draft BezCurve modifytangentpole
       move poles with knots for Bezier Curves with Degree >=3
       make bezier curves symmetric/tangent when clicking on poles by
           keeping the coordinates of the selected pole
Draft Bezier Curve: implemented Continuity Property

Draft: allow continuity on closed Bezier curves

Draft: BezCurve bugfixes
    - smoothBezCurve
    - edit mode
    - avoid splitting points into segments as long as degree is zero
    - increase the continuity when closing curve
    - closed berzier curves
    - Catch modifications of continuity of first and last knot on open curves
Cosmetic change - remove "######" placemarkers