Expose an option for whether we hide the URL bar/browser chrome in iOS and Android

[toddparker]

We currently try to hide this by scrolling the page which can introduce glitches in some scenarios. In iOS6, if a page triggers the reader feature, the URL bar will hang over the top of the page for up to 10 seconds as it parses the content which makes the top inaccessible during that time.

We need to introduce a global config option to turn this hiding behavior on and off. It's not needed at all in a hybrid app since there is no chrome within a webview.

[jaspermdegroot]

Closing as fixed by ee50437