Cleanup and some restructuring

Save the configuration before exiting so that grid choice is preserved.

Area selection! This sure was a *pain* to add.

Added panning to GL view, added action for resetting angles, zoom and pan

Use mouse wheel for zooming instead of pressing the mouse button and detecting vertical movement.

Show an error message box when main file loading fails.

A saving failure is a critical error, not a warning and should be drawn as such

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mercurial