Don't save empty scoreboard teams to scoreboard.dat - Fixes #244

While I can't think of any reason to do this except some REALLY weird workflow, I still added a config
to let you save them incase someone runs into issues.

scripts/importmcdev.sh

@@ -59,6 +59,7 @@ import FileIOThread
 import ItemBlock
 import NBTTagCompound
 import NBTTagList
+import PersistentScoreboard
 import PacketPlayInResourcePackStatus
 import PacketPlayInUseEntity
 import PacketPlayOutPlayerListHeaderFooter