Validate and tidy html files (rebased onto develop)



This is the same as gh-94 but rebased onto develop.

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I cleaned up the files, fixed validation errors and formatted them.

They need tested, there were some invalid tokens I have commented out, but they might have been important to some build system as markers.

Need checked by @sbesson and @hflynn

Oh, and why are there two `flimfit_downloads.html`?