Context menu for topsites added, neatened the js files, and tweaked focusing

Context menu includes "Open in new tab", "Open in new window",
"Open in incognito window" and "Never show again". Also had to modify
ContextMenu.showMenu in order to allow this: the target was the a link,
however e.target was an element inside the a link. I changed it to check
if e.target is a child of target and if so, change e.target to the
appropriate parent and show the menu.

Also, trimmed the js files so that no line is more than 80 chars long.

Finally, the user can now change focus with the tab button, but only in
the current page for visible elements.