An option for the options page...

Here's one proposal for the options page:

![snapshot](https://cloud.githubusercontent.com/assets/2641335/5061847/6b7d6ff8-6da1-11e4-80f3-e78029eef2ae.png)

- Put the "Save Changes" button and the help text in a fixed footer.  So, the "Save Changes" button is always visible, always in the same place, and at the "bottom of the page".

- When there are no changes, the text in the "Save Changes" button says "No Changes".  I sometimes find it difficult to tell whether the button is activated or not.

- `Control-Enter` anywhere on the options page saves all options.  (We could also make this focus `document.body`, so we're immediately good to go off and try out the new settings.)

- Add caption "Miscellaneous toggles" to visually separate the link-hints checkbox from the others.

- Make the caption for the two link-hint character sets similar.

- Make the "Show advanced options" link span two table columns, so the columns don't move when the fold is opened.

- Align the entire options page left (not centred).  This looks more like chrome.<sup>*</sup>

- Change the width of main wrapper such that it actually matches the table's width.  This aligns the right edge of the bar under the title with the right edge of the second column of the table.

- Eliminate the need for a hack in `options.coffee` by having the Exclusion Rules option table use relative layout, rather than absolute.  Now, if the y-axis scroll bar appears (or disappears), the table reorganises itself and doesn't change any of the column widths.

Addresses some of #1237.

<sup>*</sup> <sub>Although, truth be told, I couldn't get the alignment of the footer and, particularly, the space on either side looking right with the options centred.</sub>