Merge the dev material back into the main tw5.com wiki

It was getting a pain to manage the content in separate places, and I
suspect confusing for end users.

I think the best time to move the dev content out is when we’ve
established the community wiki for TW5, which is a much more natural
home for it.

In the meantime, a feature that I’m interested in exploring is the
ability to hide tiddlers from the UI based on tag. Then the tw5.com
wiki could disable all tiddlers tagged ‘dev’ until explicitly
overridden by the user.