The data returned by `Pattern.getRenderProps()` was not serializable as
we were returning `this` all over the place, thereby including marcors,
log methods, cyclic object references, and so on.
This commit changes that by implementing a `.asRenderProp()` method on
all of the various objects (stack, part, path, point, snippet,
attributes, svg) and only including data that can be serialized.
In addition, we no longer include the logs in the renderProps because
they are not related to rendering the pattern.
Instead, the new method `Pattern.getLogs()` gives you the logs.
This moves resolving of the config from the pattern constructor to the
init() method. The idea is that adding a part to a pattern is exactly
the same as adding a part to a design. In other words, late-stage adding
of parts would be no different as the config gets resolved after that.
This is currently broken in many different ways, but the unit tests
particular to this new way of resolving the config do pass.
