[TiddlyWeb] refactor tiddler parsing for reusability

[FND]

It should be considered how the tiddler-parsing code could be refactored to become a stand-alone module or project (cf.  r4tw,  PyTiddlyWiki).

This would simplify the creation of tools that interact with TiddlyWiki documents outside the browser.

Possible use cases:

• aggregation of plugin or theme tiddlers from a variety of TiddlyWiki documents
• creation of a Cook-like tool
• conversion from store-area tiddlers (within a TiddlyWiki document) to individual tiddler files and vice versa

[FND]

It appears there are three components which lend themselves to becoming an independent library (TiddlyPy?): tiddlyweb.importer, tiddlyweb.model.tiddler and parts of tiddlyweb.serializations.wiki - essentially providing the necessary functionality for a CRUD interface to TiddlyWiki documents.

[FND]

TiddlyPy? project kicked off with changeset:9296.
Currently does not take advantage of or provide alternatives to existing TiddlyWeb functionality.

[FND]

Now that TiddlyWebWiki? is an optional plugin, TiddlyPy? might not seem so useful anymore, as it includes a lot of TiddlyWiki-specific functionality.

[cdent]

Can we kill this?

[FND]

Yep; it's a speculative "would be nice" kinda thing - not actionable based on a proper use case with specific requirements.