#230 Always On Top setting for Browser window

[Steve Keen]

This will make it much easier to design a model using the Browser window. At the moment, if you click on a widget in the browser, then click on the canvas to place it, the Browser window will lose focus and, if it's behind the canvas, disappear. With this option, it's always visible.

It might be good to move (or replicate) the Browser as a command on the File or Edit menu too.