Add Vomnibar.activateEditUrl commands

Often times when I'm working on sites I want to add a query string or
modify the port number. The go up one level or root of the URL commands
are nice but they don't alow you to add or remove specifics on the
current URL.

This adds two commands that act exactly like the normal onmibar open but
populates the bar with the current URL.

I picked `ge` as the default and `gE` as the default for the same in a
new tab.
Merge branch 'feature/edit-url-in-vomnibar' of github.com:sukima/vimium into sukima-feature/edit-url-in-vomnibar

Conflicts:
	background_scripts/commands.coffee