Another round of significant fixes and refactoring in the wake of the v2 release, mostly to do with backward compatibility. One notable change: this release changes the default value for ``set`` in a lot of functions. Set is now ``False`` when it means *any set* (useful in querying functions), it is ``None`` to specifically mean *no set/setless* and of course a string with ideally (but not necessarily) a URL in all other cases.