Add rate code to rates display/ search screen

- Add Rate Code to Rates display/search screen.  This will allow users to quickly verify the rate they need to work with when they only have a rate code that may have been fed to them by a CRS 

-   Add Rate Code as search criteria on screen.  A really helpful improvement would be to add the ability to search by rate code.  If you search by the code today, it returns nil results.  This would provide the users with another quick and easy way to access a specific rate where the only information the user has is the Rate Code