[search bar] provide hint for resizing/dragging

[schloett]

User do not seem to (fully) recognize the resizing capabilities (see #37, #38). The same probably applies to dragging capabilities. Therefore, we should provide a hint directly on the content area (might be a resizing / dragging cursor in the background below the tab icons).

[mgrani]

this is an important issue. We might loose a number of users cause of this. i would also suggest to add buttons in the search bar for resizing the window (half height horizontally, full page, quater height horizontally bottom etc., see #40 )