templater: always join() over a wrapped object (BC) This is a behavior change in a sense that join() of a byte string is no longer "implementation dependent." Before, if a byte string was backed by a lazy generator, join() would concatenate each chunk with the specified separator, which seems wrong. The new behavior is always join() each byte. TypeError on join() over uniterable is also fixed.

templater: add wrapped types for pure non-list/dict values These wrapper types will allow us to get rid of some isinstance() business. A bytes object needs to support sequence-like operations (e.g. join(), ifcontains(), etc.) That's why we have two wrapper classes. Tests will be added later.