Closes #200: And lo, required fields are now required; added HTML5 form element validation for urls.
Ref #200: H5f library
Refs #200: H5f shim added
Photo thumbnails.

* multiple thumbnails with default sizes
* overloadable event to provide different sizes
* enhanced jsonSerializable view of object to provide thumbnail links in json and jsonp objects
Credit where credit is due.
POSSE links in json feed.
Making existing dependency stuff reusable.
Fixing display when requirements not met
We should parse section headings
Plugins can now specify their own requirements
Probably should use version_compare rather than strnatcmp.
PHP version compare version number compatibility
PHP version compare version number compatibility
Ability to require idno version number
Specify plugin and versions

e.g.

plugin[] = Foo
plugin[] = Bar,1.0-dev
Introducing page assets.

Page assets provide a more structured way for plugins to add resources to a page (css, javascript etc). Sure, a plugin could in this instance extend shell/head or shell/footer, but imagine this situation:

Plugin A requires a specific javascript library "Awesome.js", and bundles it with it. Plugin B also requires "Awesome.js" and bundles it. If they extended footer, Awesome.js would be loaded twice. Using page assets they'd both have a setAsset call, passing a name of "Awesome.js", so that the asset is only loaded the once.

TODO: Move core assets to this architecture
Merge pull request #221 from mapkyca/plugin_extensions

Plugin requirements. Awesome!
Merge pull request #217 from mapkyca/jsonp_posse

POSSE links in json feed.
Code cleanup, changing syndicatedAs to syndication in JSON
Merge pull request #209 from mapkyca/h5f_required

HTML5 form elements and required tags. Nice.