Fix unwanted title in ngeo displaywindow component

[adube]

For version 2.3

An issue happened with ngeo displaywindow components in desktop apps. A title was being shown with mainCtrl.displaywindowTitle as content when mouse hovering any of its content (close button, header, container, etc.)

gmfx.openIframePopup('page.html', 'My page', 500, 400);

This happens because the one of the component's options is title, which is a reserved attribute in HTML:

        <ngeo-displaywindow
          content="mainCtrl.displaywindowContent"
          desktop="true"
          draggable-containment="mainCtrl.displaywindowDraggableContainment"
          height="mainCtrl.displaywindowHeight"
          open="mainCtrl.displaywindowOpen"
          title="mainCtrl.displaywindowTitle" <------
          url="mainCtrl.displaywindowUrl"
          width="mainCtrl.displaywindowWidth"
        ></ngeo-displaywindow>

To bypass this issue, setting title="" in the template container div does the trick.

A better fix would be to change this option, but I think this should be addressed for v2.5 (as changing the name of an attribute would break the backward compatibility).

[adube]

@sbrunner I'll let you merge the branch 2.3 to master to have this fix in 2.4 as well.