Beds: Save respawn position when entering bed, only read bed spawns once

No longer require night to be skipped for resawn position to be saved
Remove constant beds.read_spawns() calls when a player joins as this
is only required once

mods/beds/spawns.lua

@@ -37,6 +37,8 @@ function beds.read_spawns()
 	end
 end
 
+beds.read_spawns()
+
 function beds.save_spawns()
 	if not beds.spawn then
 		return