menu: popups do not allow clickthrough

[clshortfuse]

Menus, currently, use an transparent scrim which is confusing for UX. If the scrim is not dimmed, then users will not know they are being blocked. Popups should close when:

• An outside element receives a click event
• An outside element receives focus
• An outside element receives a scroll event
• Window is resized (possibly)

Preliminary research shows this should be possible with a EventListener on document with the capture: true option.

The option of an invisible scrim may be optional, due to this being the default behavior in some environments (eg: Mac OS X), but it clickthrough should be the default implementation.