document types, filters, and transformations should define their own persistent ids. 

Refactoring:
* Id should become a String type.
* Document type, filter, and transoformation should extend   Identifiable interface which defines Id<T> getId();
* Id should be used in the config class to create the actual id. Id should no longer be returned.
* deal with duplicate ids (runtime exception). 
* unique ids at the xmlrouter level based on RouterConfig id. 


* add new interface  with method updateConfig(RouterConfig) by which a service updates it's own part of the router config.
* add copying of the RouterConfig. 
* efficiently check for modifications based on the id.