Redesign of the comment tab in the document footer

Implementation of one part of the comment redesign:

• Added a "View thread" button with the number of answers. Pressing it expands or collapses the thread of a comment.
• New look for quotes.
• Comment actions are displayed in larger buttons that fit more the current UI.
• Annotations and comments have now one unified look.

The redesign document contains all the information on this work and the upcoming related changes.