Add jinja title-block; style 404 page.

Add:
	templates/layout.html
		-add title block, to inherit page titles from children.

	templates/*(!layout).html
		-add title blocks accordingly,

	static/style.css
		-style revised templates/404.html.

Mod:
	templates/404.html
		-change content to simple textual error, instead of a 404 image.