Moving around some settings on the form to make it easier to deal with
Merge pull request #150 from m-x-d/3d_camera_vertical_movement

3D camera can now be moved up/down using Q/E keys.
Null textures are not tested during selection when they are hidden. Fixes #147.
Set the bounding box of model entities to the size of their display model. Fixes #148.
Merge branch 'master' of https://github.com/LogicAndTrick/sledge