Mostly styling updates but notable changes:
- Common color in theme.html, should be used by all buttons and links.
- CSS mixin to style gr-button passed to paper button (used in
gr-label-score-row, gr-linked-chip)
- Some things that look like buttons but aren't exactly buttons get
text-transform uppercase to appear like a button.
- Primary and secondary buttons are both the same color, but for now
- have not removed secondary so that it's possible to style them
differently if we decide to.
Change-Id: Ib5ef3b0fc4883cd6dfc5c38e6d954925101d531f
16721e6c8b