zooming should scale increments

[omwah]

The increments used for panning and tilting should be scaled with zoom level. Currently when moving the camera while zoomed in the movement for the left, right, up down buttons goes too far.

[LeStarch]

This now needs to be part of the generic interface. #10.

[LeStarch]

For now, implement using old way, and verify that it works given new interface.

[jbermudes]

Further testing will be required to see if this is still needed with the new continuous motion. This seems to not be an issue anymore because all movement is timed. So moving for 250ms at any zoom level isn't going to move a whole lot. This plus home presets may mitigate this issue