Better python generated code naming (#6336)

* Remove a lot of redundancy from the Python generated code.

Update tutorial to reflect new Python generated code.

* Add aliases for newly deprecated Python generated methods.

This should help with backwards compatibility.

* Fix incorrect names in deprecated comments.

tests/MyGame/Example2/Monster.py

@@ -10,13 +10,17 @@ class Monster(object):
     __slots__ = ['_tab']
 
     @classmethod
-    def GetRootAsMonster(cls, buf, offset=0):
+    def GetRootAs(cls, buf, offset=0):
         n = flatbuffers.encode.Get(flatbuffers.packer.uoffset, buf, offset)
         x = Monster()
         x.Init(buf, n + offset)
         return x
 
     @classmethod
+    def GetRootAsMonster(cls, buf, offset=0):
+        """This method is deprecated. Please switch to GetRootAs."""
+        return cls.GetRootAs(buf, offset)
+    @classmethod
     def MonsterBufferHasIdentifier(cls, buf, offset, size_prefixed=False):
         return flatbuffers.util.BufferHasIdentifier(buf, offset, b"\x4D\x4F\x4E\x53", size_prefixed=size_prefixed)
 
@@ -24,9 +28,14 @@ class Monster(object):
     def Init(self, buf, pos):
         self._tab = flatbuffers.table.Table(buf, pos)
 
-def MonsterStart(builder): builder.StartObject(0)
-def MonsterEnd(builder): return builder.EndObject()
-
+def Start(builder): builder.StartObject(0)
+def MonsterStart(builder):
+    """This method is deprecated. Please switch to Start."""
+    return Start(builder)
+def End(builder): return builder.EndObject()
+def MonsterEnd(builder):
+    """This method is deprecated. Please switch to End."""
+    return End(builder)
 
 class MonsterT(object):
 
@@ -53,6 +62,6 @@ class MonsterT(object):
 
     # MonsterT
     def Pack(self, builder):
-        MonsterStart(builder)
-        monster = MonsterEnd(builder)
+        Start(builder)
+        monster = End(builder)
         return monster