Improve trac styling - primarily for wiki

[mark]

CCing to Ed...

Problem: text in the trac wiki looks pretty rough, and IMO makes dense technical info uninviting and hard to read. Main issues are -

• No max-width for text, so lines can get mahoosive.
• Contrast and spacing between headings, paragraphs, lists etc. is too slight.
• Line-spacing is quite narrow.
• Hard black/white contrast makes things a little harder to read for most, and a lot harder to read for dyslexics.

Solution: Develop a few lines of CSS code to improve the default text formatting on the wiki.

I propose to do this as part of my Documentation work, if that's acceptable?

[ed]

approved