Support WebIntents

[bergie]

WebIntents would be a great way to connect some of the editor functionality with whatever social web services the user utilizes.

For example, insert link could choose the link based on a http://webintents.org/pick intent looking for items of type text/uri-list. This way the links could be coming from a CMS (if it registers such an intent), or from some social bookmarking service that the user uses.

While WebIntents are not yet supported by browsers, there is a JavaScript shim that we can use.