Define 'comment'.
Extracted annotation behavior from Document.Annotator.
comment -> issue.
Extracted ViewFactory class for better reuse.

E.g., used in Node Preview.
Tabula rasa.
Updated package.json
Consider subscript and superscript.
Register annotation types separately.
Started moving annotations into nodes space.
Put more annotations into node scope.
Some cleanup.
Renderer allows to create views earlier (before rendering).

The views describe their structure which is necessary to build
the Container.
Rolled back.
Helper to provide author names.
Streamline article definition.
Article cleanup.
better styles for reference types.
Implement idea/question/error markers.
Color tweaks.
remark -> remark_reference.