Minor Description
SPARQL endpoints might require or allow additional query parameters, if we want to use those endpoints with SERVICE <...> in SPARQL queries we must support query parameters and allow users to use SERVICE <...?name=value> in their SPARQL queries.
Service.java can look in the Context for additional parameters.
Parameters need to be kept separate and grouped on a per SERVICE endpoint basis (in order to avoid exposing parameter values to wrong places).
A Map<String, Map<String,List<String>>> can be uses to map SERVICE endpoint URLs to parameter-->values.
OpService.java probably needs to change (to keep the parameters separate from the SERVICE endpoint URL).
See also this thread on jena-users: http://markmail.org/thread/wc5hvr3b3uzy2mrk
