Add support for pipeline connector

In the Amazon Search Connector, we finally found an example of an output connector that needed to do full document processing in order to work. This ticket represents work in the framework to create a concept of "pipeline connector". Pipeline connections would receive RepositoryDocument objects, and transform them to new RepositoryDocument objects. There would be a single important method:

public void transformDocument(RepositoryDocument rd, ITransformationActivities activities) throws ServiceInterruption, ManifoldCFException;

... where ITransformationActivities would include a method that would send a RepositoryDocument object onward to either the output connection or to the next pipeline connection.

Each pipeline connection would have:

• A name
• A description
• Configuration data
• An optional prerequisite pipeline connection

Every output connection would have a new field, which is an optional prerequisite pipeline connection.

This design is based loosely on how mapping connections and authority connections interrelate. An alternate design would involve having per-job specification information, but I think this would wind up being way too complex for very little benefit, since each pipeline connection/stage would be expected to do relatively simple/granular things, not usually involving interaction with an external system.