Add the "quoteright" key to the list of available keyboard shortcuts.

Change-Id: I24800c28b1513b883c42d9ce1c787eaf07815b92
Implement "fill single edit" mode and map it to Ctrl-' by default.

Excel does this apparently, and lots of people want it.

Change-Id: Ia741ebb84526197d28caa323d36709e38b8f1323