This attempts to manually scale the strokes on creatures so they aren't affected by scale.
The weird thing here is that applying `vector-effect="non-scaling-stroke"` does not appear to do the trick--rather, it makes all the strokes look _super heavy_. So in this PR we scale the stroke by the inverse of whatever we're cumulatively scaling by when we're drawing something.
This fixes a bunch of bugs in our attachment-related code, and in so doing refactors things to make more sense, adds more tests, and also adds documentation.
Atul Varma