Increase the default Camera Zfar to 4000

This makes it possible to view far away objects without
having to tweak any settings. This results in a more usable
editor when working on large-scale levels.

This change should have no impact on performance, but note that
Z-fighting will be visible at a distance. This can be made less
visible by increasing the Znear value (however, doing so will cause
nearby surfaces to disappear).

This change was also applied to the editor, but it will only
apply to newly created scenes.

This also changes the default camera settings in the glTF importer
to match the Camera node's defaults.

servers/rendering/renderer_scene_cull.h

@@ -89,7 +89,7 @@ public:
 			fov = 75;
 			type = PERSPECTIVE;
 			znear = 0.05;
-			zfar = 100;
+			zfar = 4000;
 			size = 1.0;
 			offset = Vector2();
 			vaspect = false;