www: Improve layout / sidebar look, change default font, make news titles larger

Sits on top of !104 (merged)

Adds a bit of this century's flavour to the sidebar. It's easier to click around now and colours are less jarring.

Also changes the default font to sans-serif, which feels less dated, and centers everything + limits the max width, so the whole site doesn't just stick to the left side on any wide-ish screen now.

Changes header size in the News section to match the front page.

Before	After

Makes the sidebar look like buttons, not just text with a background.
Changes it so that the entire button there is a link, not just the text - feels much better to use :)
Adds a bit of padding for better UX, plus adjusts colors, borders and spacing etc.