Provide composites for strategy and processor

[jangalinski]

Scenario

Some operations that are declared in strategies and processors are very small and rely on each other. This leads to a lot of classes that have to be registered for service loading although they belong together.
To make it easier to implement a certain "flavor" of generation, it would be useful to encapsulate some features in "higher order" strategies and processors.

Wanted Behaviour

Provide abstractions for strategies and processors that return collections of result specs (list of files for example) and work on a collection of classes instead of register everything manually.