Comments panel

Narrow view to show all discussion associated with an arbitrary linked data item, to be used as a panel in the browse/detail view and as a side drawer in the full-viewport source view.

## Depends on

#11, #48.

## Constructor options

name | description
---|---
`model` | Any arbitrary linked data item.

## Rendering

If the `.model` is an `oa:Annotation`, show just a single comment thread view (#48) rooted in that annotation.

Otherwise, show a vertical list with a comment thread view for each `oa:Annotation` with a body that `oa:hasTarget` the `.model`. If the current user has permission to do so, add a "start a new discussion" button at the bottom.

## Special methods

None required.

## Events

name | description
---|---
`reply` (item, reply) | Triggered when a new discussion is started by submitting a new comment. Also propagated from embedded comment thread views.