Promoting mobile typography changes from beta to stable: Part 1

This change promotes everything except the tablet styles.
Promoting the tablet styles is slightly complicated, so I'm
moving that to a separate commit.

This commit makes several changes to the stable mode CSS:
increases font size (except in left menu), styles hatnotes,
changes thumbnail and blockquote styling, and various other
minor changes.

Change-Id: I5774ec886573f4dce06c78280e8f4b55af8462b3
Merge "Promoting mobile typography changes from beta to stable: Part 1"