Fix mglnrel::clipLine().
Merge branch 'r52' into develop

'Vertext' -> 'Vertex'.
Add ignoreStartPoint() for commands.
Add getSubType(), isVisible() and isLocked() for shapes.
Add name field of group shapes.
Add bringToBack(), bringToIndex(), getShapeIndex() and getShapeAtIndex() of MgShapes.
Add shapeWillDelete notify.
Send shapeChanged notify in MgCommandDraw::touchMoved().