Random Tree: optionally omit redundant segments

[su_v]

The attached patch adds a new option to 'Extensions > Render > Random Tree' to avoid drawing redundant segments by lifting the turtle's pen for backward steps.

Helpful for any further processing of the generated tree which doesn't handle redundant segments well (e.g. output to a cutter/plotter, or applying a path-modifying extension like 'Fractalize').

Idea based on this forum topic:
http://www.inkscapeforum.com/viewtopic.php?f=5&t=19449

[su_v (suv-lp)]

Example illustrating simple use cases with current default and with new option.

[su_v (suv-lp)]

Second version of patch to improve UI message:
 [ ] Omit redundant segments
with the original description added as tooltip:
 "Lift pen for backwards steps"
(describes how the option affects the turtle drawing the path)

[su_v (suv-lp)]

Committed in rev 14403.