Prevent controls div from being "lost" on mobile devices

[fedarko]

This is sort of a weird issue! But it's possible to zoom in on the HTML page and then scroll down on the actual HTML page, which can result in the top "controls" div being left out of the viewport.

On a computer this is fine (you have a scrollbar since, for now, the body CSS overlap value is left to its default value), but on a mobile device you don't have something like that, and scrolling up will just result in the cy div panning up. Which messes up the user interface. Also, on touch devices it's somewhat easy to accidentally zoom in on the HTML page instead of the cy viewport.

I guess the solution to this is just disallowing zooming on the HTML page using the <meta> tag, I think—that still allows zooming in the Cytoscape viewport, and the control panel text is all sized relative to 0.75 em so it'll adjust with the user's font size.

[fedarko]

Yeah, this has basically been superseded by #120 and #68 since the entire "control div" structure has changed. Closing.