Minor fix: update id to known value

When no events exist, use a known html id for the element
instead of what evaluates to `undefined` in javascript.
Comments now have topics

Update Comment model and CommentController to support
the notion of topics, which is as simple as setting
the `topic` flag to true.  For all child comments of
topics, they must set their parentId to that of the
topic.

From the comment model:

/**
 * Comment
 *
 * @module      :: Model
 * @description :: Comment data model for nested comments on
 * projects and tasks.
 *
 * Comments are organized hierarchically as follows:
 * Topic
 *  |-- Comment
 *     |-- Reply
 *
 * All comments MUST have a projectId or taskId.
 *
 * Topics are the first level, and have no parent (parentId = null).
 * When created, the topicId should be true.
 *
 * Comments are children of topics.  Comments should always have a
 * parentId that is equal to the topicId.  topic should be false
 * (or unset).
 *
 * Replies are children of comments.  Replies should have the topicId
 * set to the main topic.  The parentId should be the id of the
 * parent comment.
 */
Connect UI to comment topic feature

Make changes to the UI, UI views, and UI controllers to
support the notion of discussion topics.

The "new topic" button drops down an input box for the
topic content.  This is then saved via an AJAX call and
the collection is refreshed.  DM: please fix this to
use the appropriate collection calls if it shouldn't work
this way, which is outside the backbone framework.

The comment-list-wrapper now renders all of the comment
UI, including the header.  Inside of each comment-list,
when there's a topic, it renders the topic and then
the comments for that topic, then a placeholder for
the comment form at the end.

After the view is rendered, the new comment sub view
is rendered for each of the topics and inserted into
its comment-form-wrapper.  The new comment view has
been modified to be passed the topicId (parentId)
as an option, so it can relay that to the backend.