Process some FormInput against a FileOpener, which provides access to the user Session and optionally a specific file.

• A FormBinding maps a FormProcessor to a FileOpener
• A FormBinding is referenced by a UID
• Form inputs must be prefixed with this UID to reach the processor
• IFormProcessors are bound within a pipeline.
• UID is available to XSL or Velocity templates executed in the same pipeline
• Form action is non-specific: any input received in a request to HyperContent will be processed if the binding prefix is found in the user's session