Transition to editor's draft of spec for Image Capture

The first implementation of <app-media-image-capture> was based on the working draft of the spec. The latest implementation is now based on the editor's draft.

Docs and annotation updates

• Relocates @enum annotations so closure can find them.
• Adds documentation about using <app-media-stream> for screen capture.

Fixes app-media-devices @type annotation

v0.5.1

v0.5.0 -> v0.5.1

Fixes @type annotations in several files.

v0.5.0

v0.4.0 -> v0.5.0

Adds enum annotations where appropriate

v0.4.0

v0.3.0 -> v0.4.0

More type annotation fixes.

v0.3.0

v0.2.0 -> v0.3.0

Fixes type annotations for closure compiler

v0.2.0

Whoops.

Experimental release of app-media elements.

Refer to README for information on this component.