Improve Standard and Core Field Documentation

And perhaps more completely, by

Which yields these values:

_canonical_uri creator list-after source
_is_skinny current-tiddler list-before stability
author dependents modified subtitle
bag description modifier tags
caption draft.of module-type text
class draft.title name throttle.refresh
code-body footer parent-plugin title
color hide-body plugin-priority toc-link
component icon plugin-type type
core-version library released version
created list revision