Deprecate GeneralStrands

Before #123, GeneralStrands had never been used because it rendering gave an error and always had. Moreover, if you’re varying the offset, you’re varying the width of the traces, and unless you're going for something artistic I don't think you ever want that. Parallel paths with variable offset should probably always be drawn using a tapered RouteChannel and SingleChannelRouting instead.

Start by locating GeneralStrands and reviewing issue #123 to understand the rendering failure and its current use. Then inspect RouteChannel and SingleChannelRouting for the stated alternatives. Done means GeneralStrands is deprecated and the recommended replacement is clear.

Written by the indexing model from the issue text.