3 col transitions

...e third column

Hi Roman,

In preparation for the visualization and other widgets being shown in the middle of the results page, I improved the expanding column interaction on the results page in a few ways:
* made 3rd col collapse into first col when screen is tablet sized
* added a model to keep track of which columns are open and which are closed
* now there is a method for the page manager to call to make the center column full width or return it to default size.

I did two things that you might not like : the page manager 3 column view is listening to the window resize event--I think I should change this to a single app listener on window events that other widgets can subscribe to.
I also had the problem that right now the "show" event is being triggered on page layouts before they are actually in the dom, so for now I re-triggered the event in the master page manager's "onSelectedChange" function. I also added a "detach" event.
i prefer: model.attributes.object.detach()   -- or 'close' -- that way, the controller can decide what needs to be done