Blender Git Loki

Added new line style options for sketchy chaining of feature edges.

The default chaining option is now called "Natural", while the new chaining options
are "Sketchy: Topology Preserved" and "Sketchy: Topology broken". The latter two
options allow for generating chains of feature edges with a sketchy multiple touch.
The "Sketchy: Topology Preserved" option takes account of the topology of objects
in the view map, while the "Sketchy: Topology broken" ignores the edge topology.
The "rounds" option specifies the number of rounds in sketchy strokes.