Starting to make the members of $tw.Wiki be private

We want to avoid plugins from directly accessing the tiddlers hashmap.
Later we’ll do pluginTiddlers, pluginInfo and shadowTiddlers.
Freeze array or object tiddler fields

Previously object fields like the tags array weren’t frozen.
Make shadowTiddlers, pluginTiddlers and pluginInfo be private to the Wiki object constructor
New error message text for recursive transclusion error
Fix crash with headings

`this.match[1].length` can get overwritten when we parse the content of
the heading
Update transclusion wikitext syntax to allow a template without a target tiddler

This allows us to transclude a tiddler without changing the current
tiddler with `{{||MyTiddler}}`.
Add chinese translations of ClassicWarning section for TWC tiddlers
Merge pull request #493 from BramChen/master

Add chinese translations of ClassicWarning section for TWC tiddlers
New architecture diagram and docs updates
Fix bug with plugintiddlers filter operator
Fix typo
Stop using obsoleted "-moz-border-radius" and "-webkit-border-radius" properties

Fixes #480
Explicitly blacklist unsafe elements, starting with `<script>`

Are there are any other elements that might be considered unsafe?
syncer freeze fix
plugin development with github and node.js
plugin development doc
Italian translation available

Add italian translation
Make more core strings be translateable

Now we’re translating strings that occur in JavaScript modules.

Partially fixing #491
Merge pull request #498 from buggyj/plugindocumentation

Plugin development with github
Merge pull request #496 from buggyj/syncer

syncer freeze fix