Keeping metadata when apply functions to data

We want a "framework" that keeps the metadata (eg, TR in a list of fMRI images) when transformations are applied to data.
However, we also want to build and deal with simple functions that take objects as simple as possible, and don't drag the metadata around (for instance to avoid sending the metadata on each node of a cluster.

A code example in the blue prints shows a way of decorating functions to do this. Providing a module with non decorated functions, and one with the decorated function will allow the user to use the functions outside the framework, or inside the framework.