Isomorphic lhs are not handled correctly

[rhz]

If two isomorphic lhs are written in different order, the mapping from agents in the lhs to agents in the mixture is wrong, it needs an "adapter". This probably happens because the embedding is made using the first pattern registered for that iso class but indices are stored in actions using the lhs own indices rather than the representative's indices.

Ideas:

1. When we discover that a pattern belongs to an iso class, we can generate a mapping from the pattern to the representative
2. Make Action.apply really agnostic to ordering
3. Maybe even forget about ordering in Patterns?