Refactor android code to use LargeScreen layout instead of MobileLandscape

[DavidRGriswold]

This is a first step toward adding the Small Screen Position feature #332 . It removes the invisible internal "Mobile Landscape" layout and replaces it with "Large Screen Layout", but uses an #ifdef and new default proportion setting to modify it on Android so it looks identical to the old MobileLandscape layout.

This is necessary to eventually expose the small screen position and large screen proportion settings on android UI.

For now, the only user-facing change will be the menu saying "Large Screen" instead of "Default" for the layout on mobile. That can be changed back if desired.