The main output routines now more or less work.

Known issues:
- InsetLine normally appears in a standard environment, which puts <hr /> inside
	<p>, in violation of the DTD. I guess we could close the paragraph and then do
	the <hr />, but isn't there a better solution? There's actually a LyX bug here, 
	I think, since a line surely ought not appear in a normal paragraph?
- The code that manages the nesting of tags is pretty primitive. It needs a lot
	of work.

These insets are basically done, though there are probably issues here and there,
	and there are even some FIXMEs:
	Branch, Collapsable, Footnote, Hyperlink, Label, Line, Note, 
	Newline, Newpage, Quotes, Space, SpecialChar

These insets probably do nothing:
	OptArg, Phantom

These insets work but still need work:
	InsetBox: We need a Length::asHTML() method and the like, but it basically works.
		though the CSS isn't there yet.

These insets do not work but should be completely straightforward:
	Caption, Flex (uses collapsable)

These do not yet work and need some attention:
	InsetBibitem: Should be fairly straightforward, in itself, actually.
	InsetBibtex: We should be able to collect the keys of references in
		validate() and then use our parsed information to output some sort of
		bibliography. Formatting is another question, but here again we could
		try parsing the bbl file.
	InsetCitation: I think we'll want to do something here involving reference keys.
		Maybe for the beginning, we should just do everything numerically, but even
		that will need a bit of work. Validation is our friend, presumably.
	InsetCommand: By default does nothing. That may be right?
	InsetERT: It's not entirely clear what it's best to do here. Maybe output it
		verbatim. Perhaps wrapped in some CSS. (What else would one expect?)
	InsetExternal: I don't understand these so am not sure what to do.
	InsetFloat: This will need some work, again because I do not really understand
		what these are meant to do. Presumably, we'll just use a div or something, but
		it's not clear what subfloat means, etc.
	InsetGraphics: This should be fairly straightforward, but I'll need to learn a bit
		about export formats, etc, to get it completely right. We'll also want to make
		some use of the params, eg, on width and height. I guess there is also some
		issue about converting the graphics formats?
	InsetInclude: I think we just want to include it, straightforwardly. Probably will
		base this more on the latex() routine, then. Another possibility, maybe with a
		flag of some sort, would be to do it as a separate file, to which we link.
	InsetIndex: Not clear whether to do anything with this or not. Certainly it's an 
		"advanced" case.
	InsetInfo: Probably skip it.
	InsetListings: Probably just output it as <pre>.
	InsetMarginal: Fine, but will need CSS.
	InsetNomencl: Also "advanced".
	InsetRef: Presumably, this is an internal link. But what should the text be, and how
		should we get it? Probably some validation thing again, where labels tell us where 
		they are. Alternatively, we could parse the aux file.
	InsetTabular: This shouldn't be too hard, but will need doing.
	InsetTOC: Here again, validation might do the trick, but I'm not sure. Or perhaps some
		kind of post-processing? Another option, maybe the best option, would be just to use
		the information we already have in the TOC.
	InsetVSpace: This will be easy, once we have the Length::asHTML() method.
	InsetWrap: This should be simple enough, probably a div and some CSS, but I'm not sure
		precisely what this is supposed to do.
There seems not to be much here for math, so that will take some doing.