Add an editing interface for Component Block Presenters

Since we're looking at a system that would allow auto-ingesting components as Drupal plugins (probably blocks), we should also look at implementing an editor interface for Component Presenters.

An existing module implements this functionality: https://www.drupal.org/project/patternkit

Roadmap Suggestion:

• New plugin type: Component, auto-populates based on component.yml definitions inside Extension (module/theme) folders
  • Includes several default components based on commonly used HTML templates as examples
  • See #2707849: Allow a component library to define asset libraries
• New plugin type: Presenter, code snippet or twig inline template that can take input (field w/ Component formatter, view Component display, other presenters etc.) and outputs a string or array to a Component plugin
  • Includes several twig function-based Presenters (uppercase, lowercase, trim, if/else, choose array value etc.)
  • Includes a 'custom' type that uses the typical theme system template suggestions, allowing you to hand-write your own presenter, similar to how we often do it now
• New field formatter plugins: Component, transforms most field plugins into string or array values
• New Views display plugin: Component, transforms views output into a string or array of values
• New widget plugin: Node-based Graph Editor, allows connecting Presenter plugins visually together to generate output HTML, http://codepen.io/cyb_tachyon/pen/VPygVW as an example
• New auto-discovery block plugin: Component Block, auto-populates based on Component plugins - this is essentially the same plugin that's already being worked on here
  • Block plugin uses the Node-based Graph Editor widget to allow Visual Node-based Programming of Fields connecting Presenters in chains to Components

Some discussion points:

• Do we need a Node Graph Editor for presenting the data model to front end components? It's complicated UX for a relatively simple process (data mapping). Is there a better solution that covers most use cases?