Use partialCached to avoid any perf penalty.
TODO: limit the scope I pass to them.
I noticed a teeny tiny perf improvement after doing this, probably
because now some giant data structures only need to be generated once.
The site now has polygot markup and can handle both XHTML5 and HTML5
parsing rules. My staging site will be XHTML but my main site will be
HTML5, just in case of parse errors.
If other tools (e.g. LightHouse) end up supporting XHTML5, I'll consider
switching the content-type to XHTML.
Split up some verbose and repetitive templates to use nested templates.
Cache some templates that don't need to be re-built every time.
Reading time: switch "a" to "an" when followed by the number "8".
Improve whitespace alignment a bit.
