[Bf-python] BMesh python api proposal.

[Dima Glibitsky]

> It's a bit inconvenient to do this, but it's still just two lines of
> code to create and delete the datablock. What are you expecting the
> function obj.get_visible_derived_mesh(scene) to do different? Be more
> efficient, have some extra functionality?

Yep, simply as a concern for efficiency. If user works with hi-res
objects, the time/memory spent on datablock copying just seems to be
wasteful, since the data is already present.