New animation class and big improvements to MapCube plotting

This is something I spawned over christmas originally with HyperMap in mind, hence it's a lot more complex than it needs to be for this use.

What is contained here is the following:

* A new general framework for interactively exploring arbitrary data, where there are one or multiple sequences of images.
* Two applications of this framework:
* One for MapCube
* One for numpy ndarray's