WIP: Crackle operation

[yaxu]

Proof-of-concept implementation of crackle weave, where a motif is repeated along a path, with 'incidental' warps added where needed to connect motifs.

It seems to work well, but marked as WIP as it needs some polishing. It would be good if e.g.:

• the standard crackle weave motif was used if that inlet isn't connected
• someone more familiar with AdaCAD and weaving paradigms looked over it ! For example probably it would be more weaverly if the motif was placed relative to its bottom rather than top?
• the 'add incidentals' argument wasn't ignored
• I had a proper look at the rules for adding incidentals or removing ends, perhaps adding configuration options for changing them

Plus it needs documenting!

Ref:

• Ralph Griswold - Pattern book, and guide part 1, part 2, part 3
• He references Harriet Tidball 's explanation which tied it together for me
• He also references Berta Fray's "Designing and Drafting for Handweavers" for crackle rules, which I couldn't find online but have ordered a hard copy !