Extend makeTranscludeWidget

Add support for specifying the filename, and the fallback content
within the transclude widget that is used if the transclusion target
isn’t found
Fix problem with refreshing modal dialogues

Previously any refreshing of the content of a modal would cause a
crash. The problem is the way that we steal the root widget for the
render trees used in the modal. The root widget is tied to the
container DOM node for the main content area, which isn’t actually a
parent of the modal DOM nodes, hence the confusion for the refresh
mechanism.
Fix issue with localStorage error on Firefox

Firefox raises an error if window.localStorage is accessed when cookies
are disabled:

https://bugzilla.mozilla.org/show_bug.cgi?id=771890
Merge remote-tracking branch 'upstream/master'
Docs update
Merge pull request #675 from BramChen/master

Typo
Refactor theme tweaks as individual tiddlers

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.
Merge remote-tracking branch 'upstream/master'
Refactor animation easings
Add support for story backdrop and frontdrop

Allows elements to be added above or below the story river
Merge remote-tracking branch 'upstream/master'
Hide page background when printing
Further refinements to print stylesheet

Try this @giffmex
Merge remote-tracking branch 'upstream/master'