[dev] surf patch: bind keystrokes to snippets of Javascript

The attached patch lets you bind keys to small lines of Javascript to
run.

The intent is that the usual ~/.surf/script.js defines various methods,
which are then run by the bindings. This is much cleaner than having
script.js create its own event listeners for keybindings going outside
surf's own system.

-- 
\  Troels
/\ Henriksen