Update 'Object Type Definitions'

Object-Type-Definitions.md

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+Object types can be defined like this:
+
+```
+objt ro Rectangle:Obj
+	ro x:Int
+	ro y:Int
+	ro width:Int    16
+	ro width:Height 16
+```
+
+The "type" of an object type definition is what object it inherits. Most objects
+will inherit from Obj, which is a blank object.
+
+Object definitions have a list of members, preceded by a permission. Members can
+have simple or complex initializations, or none at all. These act as the default
+values for those members.