Provide application-specific scaling unit factor

[eile]

Add config attribute to have the application provide a scaling factor if the rendered model is not to be visualized in 1:1 scale. Use case: The application visualizes something small (neurons ;) ) or very big (planets) and still wants to visualize this in a VR environment where the frusta are given in meters. This scaling factor is then applied to the wall and projection, the eye_base and potentially the translational part of the head matrix.

[eile]

Should actually be a view attribute

[eile]

API:

void View::setScale( const float scale );
float View::getScale() const;
#define EQ_MM 1000.f
#define EQ_CM 100.f
#define EQ_DM 10.f
#define EQ_M   1.f
#define EQ_KM 0.001.f

[eile]

Works