Don't make Tags a required AutoScalingGroup property

Despite the documentation saying this is required, none of the examples
have Tags in them. So we'll make this an optional property for now..
Add new UpdatePolicy attribute

Add the new Updatepolicy attribute which can be used with
AWS::AutoScaling::AutoScalingGroup. Might need to rethink how
these attributes get attached but for now we'll leave them as
"special" properties.