Inkscape to OpenSCAD converter v7

A series of mods to [Dan Newman's](http://www.thingiverse.com/dnewman/about) excellent [paths2openscad](http://www.thingiverse.com/thing:25036) program.
These include:
- separating the paths themselves into variables so they can be used in other ways.
- adding helper functions to enable them to be rescaled easily.
- automatically saving unclosed lines as lines and not as joined up closed curves.
- adding an option to save any closed curve as a line if desired.

For Inkscape 0.91 and above