3D camera focusing

Changes the way 3D camera is positioned during "Center 3D View on Selection" / "Center All Views on Selection" actions.

Aaaand also "Select wall width" window setting can now be applied using Enter key (because I still haven't fully figured out the way Git works...).

Aaaaaaaaaaand also adds missing click handlers in SettingsForm...

And also textures can be applied by double-clicking a texture in texture lists in Texture Application form...