Rename chain namespace into operation

[leodido]

The term "chain" seems to suggest a set of operations executed in a predefined order.

Generally speaking, the scope of Facade pattern is to provide a simplified interface to a more complex and underlying collection of operations, so making software easier to use.

We do not want to represent the underlying operations architecture nor organization (that, by the way, are always sequential), but we simply need (imho) to wrap them in a more concise and intelligible way.

Therefore I suggest to rename Chain namespace into Operation.

[leogr]

I agree.