[Developers] Updating the "Transmission Type" type

[Bryan Cheung]

We currently have a "Transmission Type" type that is unused.  It is  
the classification of automotive transmissions, or essentially manual  
or automatic transmission.  I'd like to clean it up a bit and link the  
topics to the transmissions.  I'd also like to add a  
transmission_classification property to trim_level - this is a slight  
denormalization, but it will allow users to search for any type of  
trim level that is automatic or manual.

More details can be found at https://bugs.freebase.com/browse/ 
DA-546 .  I'd like to make the changes next week; as always, if there  
are any strong objections, please let me know.

Bryan