Release 2.2.0

Boost on real sites (plan T11):

• boost.js starts itself from its script tag: <script src="/shared/boost.js" data-main="#main" defer> (optional data-prefix, data-exclude="/a/,/b/"); the controller is OVBoost.controller. OVBoost.start() still works.
• A swap also carries the new page's <body> class (page-type classes).
• navbar.js follows boost: on ov:boost:load the bar re-renders (active links, a sign-in that returns to the new page) and records the new page in the signed-in person's history.