SVGLoader Additions

[jonobr1]

Untested additions:

• Added Q, T, and S commands to the path parser
• Added Circle and Ellipse node parsers
• Added Line node parser
• Added Polygon and Polyline node parsers
• Added a variable control to have a reference of the previous point's bezier handle point. I think this could be referenced from the THREE.ShapePath somehow, but wasn't entirely sure.
• Added getReflection function for getting the coordinates of the reflected point about another point. More info

Still need to add:

• Rounded Rectangle node parser
• A command in path parser

#13478

[mrdoob]

Thanks!