Landing page templating with wp.template.

Got rid of the icanhaz templating and using wp.template instead.
More whitespace in jp.js
Template instead of jQuery html injection in jp.js

Inject the contents while templating, instead of building the containers and
injecting the contents afterwards.
Activation and configuration on landing page cards

Added a link to activate or deactivate a selected feature or configure it
directly from the landing page feature cards.
Landing page module actions to top of the modal.

Moved from after long description to the top bar left of the X (close).
Removed unneeded deps from wp_enqueue_script.

The landing page JS doesn't need Backbone, nor does it need underscore (since
it's a dependency of wp-util)
Merge pull request #799 from Automattic/enhance/landing-page

Landing page update