Emulate minimize for windows in the browser

[Dillonu]

The the Browser runtime, the windows currently don't support the ability to minimize.

To solve this, we should currently minimize windows down to the bottom of the launcher window, and list them in adjacent divs with the window title displayed. Clicking on them restores them. There should be a close button.

Behind the scenes:

1. We build in a "toolbar" area at the footer of the launcher.
2. When a window is minimized, its iframe is hidden, and a div is added to the toolbar
3. Clicking the div restores the iframe, and removes the div.
4. Clicking close will remove the div and iframe.

Future items:

1. Allow the toolbar to be themed.
2. Allow the toolbar to be disabled in favor of the user's implementation (minimize then simply becomes a hide operation).