Throw error on duplicate

Under expected circumstances, a duplicate `MemberInfo` key should not exist. This will happen, however, if the `new` keyword is used on a member of the _current_ class (as opposed to a _derived_ class). In that case, an error will occur. This should not happen; if it does, the developer is warned about the duplicate key with a specific error message.

Author: JeremyCaney

Ignia.Topics/Reflection/MemberInfoCollection{T}.cs

@@ -40,7 +40,12 @@ in type.GetMembers(
           BindingFlags.Public
         ).Where(m => typeof(T).IsAssignableFrom(m.GetType()))
       ) {
-        Add((T)member);
+        if (!Contains(member.Name)) {
+          Add((T)member);
+        }
+        else {
+          throw new ArgumentException("The Type '" + type.Name + "' already contains the MemberInfo '" + member.Name + "'");
+        }
       }
     }