Bird's Eye View - Spectator System

1. Added server-side cvar birdseyeview_spectator_only (Default 0), birds are only visible to other spectators.
2. Added server-side cvar birdseyeview_screensplat (Default 1), enable screen splats when a player is hit by bird droppings.
3. Increased delay before bird dropping entities are removed without impacting anything, they will now work for longer drops.
4. Droppings are less likely to apply two different decals on impact.

1. Added server-side cvar birdseyeview_screeneffect (Default 1), enabled the screen effect while in bird mode.
2. Potential fix for a Ulib compatibility error.
3. Fixed a rare clientside error when switching to bird mode in DarkRP.

1. Fixed some animation issues while gliding with the Duck key.
2. Removed the delay adjusting bird speed when pressing the Duck key while on the ground.
3. Bird droppings will now spawn below the bird by a few units.
4. Bird droppings now disappear after a time if they do not collide with anything.

Initial version.