Provide examples for embedded Process Engine (to enable doc)

As discussed in our meeting KrisVerlaenen dmarrazz@redhat.com

Also as I mentioned to you mmacik@redhat.com please look

rhn-support-hjoy FYI

Enrique: as discussed please help us get the following examples:

• A simple plain Java example for testing processes, with Runtime Manager and a human task handler
• A plain Java example of production-class embedding of the engine, with the Process Engine Services 
• A SpringBoot embedding example - this could draw from what we have on start-jbpm and from Jeffrey's example: https://github.com/Emergency-Response-Demo/process-service

We need to make the example available in a public repo that has branches or tags which are fixed at FINAL releases, this is needed so I can refer to them from the docs.

mmacik@redhat.com said that existing test cases for plain Java might be relevant too.