Core: change how required versions work, deprecate IgnoreGame (#426)

`AutoWorld.World`s can set required_server_version and required_client_version properties. Drop `get_required_client_version()`.
`MultiServer` will set an absolute minimum client version based on its capability (protocol level).
`IgnoreVersion` tag is replaced by using `Tracker` or `TextOnly` with empty or null `game`.
Ignoring game will also ignore game's required_client_version (and fall back to server capability).

worlds/sm/__init__.py

@@ -69,6 +69,10 @@ class SMWorld(World):
     remote_items: bool = False
     remote_start_inventory: bool = False
 
+    # changes to client DeathLink handling for 0.2.1
+    # changes to client Remote Item handling for 0.2.6
+    required_client_version = (0, 2, 6)
+
     itemManager: ItemManager
 
     locations = {}
@@ -167,11 +171,6 @@ class SMWorld(World):
         create_locations(self, self.player)
         create_regions(self, self.world, self.player)
 
-    def get_required_client_version(self):
-        # changes to client DeathLink handling for 0.2.1
-        # changes to client Remote Item handling for 0.2.6
-        return max(super(SMWorld, self).get_required_client_version(), (0, 2, 6))
-
     def getWord(self, w):
         return (w & 0x00FF, (w & 0xFF00) >> 8)