* Made the link between "names" and "properties" explicit (I only figured it out by reading the TextReference documentation)
* Documented named property manipulation through ActionWidgets.
The trouble with the previous approach of storing several settings in a
single data tiddler was that it made it hard to introduce new settings.
Users who already have a custom copy of the settings/metrics tiddler
wouldn’t get the default settings. The new approach uses individual
tiddlers for each setting.
This commit also introduces a new theme tweak for the cutoff width for
switching between responsive views.
