Stop using pre-defined landscapes

[Pintokitkat]

As Stellarium works so well on phone and tablets, why not use the devices camera to show the real landscape around the user? The ability to differentiate the foreground from the background of an image seems to have been cracked, so painting the Stellarium view over the background (effectively the sky) would give a much better experience than the current 'glass shots'.

[10110111]

1. Stellarium desktop doesn't work on phones or tablets.
2. Stellarium Mobile already supports using the camera to show the real landscape (Augmented Reality mode, since v1.14.0).
3. Stellarium Mobile is a separate project, and this repo is only concerned with desktop Stellarium.