Refactor camel-jbpm so that it communicates only via Rest API

Please refactor caml-jbpm so that it communicates only via Rest API. At the moment (Fuse 7.4), the component camel-jbpm brings BxMS dependecies and it is working only on a runtime with KIE server.

Note that this is applied to consumer part - the producer is implemented via Rest API.

The goal is to communicate with BxMS processes only via Rest API. This will simplify any future integration between Fuse and BxMS on any runtime.