Introduce NO_MARBLE define, make GlobeGPS a dummy

Some users have requested a way to build subsurface without marble.

This hides all traces in the ui and creates a GlobeGPS-dummy thats
just a QLabel saying that marble is disabled, in case its shown
somehow. The dummy is there so we can just ignore the fact that marble
is disabled in the rest of the code.

Fixes #394

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Introduce android specific file

This contains a first stab at Subsurface platform interfacing code for
Android, and surrounding parts.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Disable marble on Android

marble uses webkit, and thats not compatible with Android.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Remove usermanual when building for Android

Our usermanual is based on webkit, and thats not supported in Qt for
Android. We should probably replace it with a Android native webview
somehow.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Remove printing when building for Android

Qt for Android doesn't support printing.

Signed-off-by: Anton Lundin <glance@acc.umu.se>