Add ability for link macro to link through a given field

This is a bit of a hack, and a more harmonious way of doing this is
planned
Allow template overrides for the story
Restore SubStories sample
Include URI in TiddlyFox confirmation prompt
Update version info
Improve TiddlyWiki classic detection

We were missing older versions of TiddlyWiki
Separated out the version check to make it easier to test
Mark TiddlyFox as compatible with Firefox for Android

Experimentally
Removed TiddlyFox

It has moved to https://github.com/TiddlyWiki/TiddlyFox
Added support for PDF images
Fixed the view macro to fail silently if the target tiddler doesn't exist
First commit of TiddlyWiki5 in the Sky for Dropbox

This is a new build of TiddlyWiki5 that pulls it's content from a
Dropbox App folder.

(This naming strategy is seeming increasingly stupid).
Several fixes

1. Made crypto module optional
2. Moved hasOwnProperty into boot kernel
3. Fixed handling of modules in the browser
Added plain module serialiser

Needed when we pack lots of modules into a single .js file
Updates to tw5dropbox
Reorganising tw5dropbox
Started refactoring tw5dropbox into separate wikis

One wiki for the hosted shared app, and one for the wiki app that is
created in the dropbox sandbox
More rearchitecting of tw5dropbox
Removed extraneous console.log
Compute wikiname from document URL