Add configuration to insert apple-mobile-web-app-capable

<meta name="apple-mobile-web-app-capable" content="yes"> would be added to document head with this configuration setting enabled. It's not universally applicable, so making this configurable only makes sense.

This is iOS only, runs the browser in full screen mode when added to the home screen. https://developer.apple.com/library/safari/#documentation/appleapplicati...