Polish look and feel. Ref bug 959863.

What do you think, Schalk? I'm looking for any place where I clumsily knocked over any undocumented CSS tower you built and also anything else that greatly offends you.

* Change yellow-green color scheme to a more neutral gray.
* Remove thick black band separating search panel from the rest of the page; it draws my eye.
* For the same reason, recolor folder listing table header.
* Darken Switch Tree menu enticingly on hover.
* Tighten up leading on code listings so it’s a little easier to see the shapes of block structures.
* Rig result snippets and code listings so mousing over a line highlights the line number as well. This makes it easy to find the number of a line without having to distractingly zebra-stripe the whole thing. (I’m willing to zebra-stripe the folder listings because they’re not as mentally demanding to read.
* Make the entire line-number table cell in code listings clickable, not just the line number itself.
* Put the tree name in the search box placeholder text to reinforce that you’re searching only the selected tree.

More to come.