Tweak the HTML and CSS of the new search

There was a basic problem that FF on my system was enforcing user agent
styles on the button tag, which made it difficult to properly size the
clear button with simpler styles. Enforcing a font size for all the
elements underneath the search container helped.

FF also didn't expand the input to take available vertical space, which
was the cause for the 2em height setting. Using a line height on the
search container and some padding on the input helped. Line height on
the input itself works nicely, but WebKit seems to have some issues
with line heights on input boxes [1].

I finally got everything looking pretty much the same in both FF and
Chromium here.

I also simplified the markup just a bit and removed styles that appear
to be redundant.

[1] https://code.google.com/p/chromium/issues/detail?id=47284