Verify matching jumps colored_brothers on first eclass

[eytans]

I changed the EGraph API to use search, search_eclass, and colored_search_eclass. Each has different assumptions, but in general search should also return colored results. Therefor, it should jump to colored equivalences from the first eclass we are searching in.
Should also check what are the assumptions for colored_search_eclass, and add tests accordingly.