Header block name should be bold.
User comment block changes:

 * Moved timestamp to below username
 * Site title/url is displayed next to timestamp if it is available. Also tappable and loads Url in a web view
Layout tweaks to get margins matching up.
Added url to `CommentTableViewCell`
First attempt at removing gap between header and content.
Fixed storyboard/nib framing warnings.
NotificationDetails: Updates Header Separator
Updates NotificationDetails separatorColor
Fixes separator inset on iOS 8.

Props @jleandroperez for the fix!
Removed duplicated comment.
Fixed a broken constraint.

Changed top edge constraint for the `Dynamic Height TextView`
Wiring NSString Helper
Merge remote-tracking branch 'origin/develop' into issue/2716-user-comment-design-changes
Merge pull request #2734 from wordpress-mobile/issue/2716-user-comment-design-changes

Updates to comment view design