Options; use consistent capitalization.
Options; add help text for scrollStepSize.

No help is really needed.  However, the gap where the help text should
be looks ugly.
Options; restyle exclusion rules.
Options; release focus on clicking advanced.

When the show/hide advanced options link is clicked, it gains the focus,
and the URL is displayed by chrome in the bottom-left corder of the
window.  This partially obscures the footer, so we immediately blur the
link.

Also, same for the "show help" link.
Options; Reintroduce min-height for exclusion rules.

We need to keep *some* minimum height to avoid the help texts colliding.
Re-jig options page and re-factor styles
Automatically insert "leave empty" message for nonempty options
Fix the alignment of the save button in options
Align options page help text with the top of the cell
Style tweaks for options page footer