RESTWorkItemHandler matches content type for equality

The RESTWorkItemHandler matches the content type of the response for equality. It means that response with content type set to : 'application/json; charset=utf-8' is not parsed correctly, even if the response is a valid json. The public github api is an example of such an api that is returning mentioned content type.

It should be enough to change these two lines:

• https://github.com/droolsjbpm/jbpm/blob/master/jbpm-workitems/src/main/java/org/jbpm/process/workitem/rest/RESTWorkItemHandler.java#L360
• https://github.com/droolsjbpm/jbpm/blob/master/jbpm-workitems/src/main/java/org/jbpm/process/workitem/rest/RESTWorkItemHandler.java#L364