Toggle expand/collapse of all folders in browser

[distefam]

It would be helpful to be able to toggle expanding and collapsing folders in a browser.

I organize many of my projects into high-level folders that represent GTD "Areas of Focus". Viewing all of my projects in the projects browser displays all folders as collapsed by default, which makes non-area-of-focus projects appear more prominently than those within areas, exactly the inverse of what I'd like to see.

While it is possible to toggle the expand/collapse state of a given project it would be useful to be able to do it "globally" for the entire visible contents of the browser. This would also possibly address #209

[NorfairKing]

PR welcome!