Unify Drools and jBPM execution servers

This is a placeholder parent ticket for the merge of the code from Drools and jBPM execution servers into a single server.

The new server should be standalone, free of UI code, support remote interfaces, and comply to all requirements from both Drools and jBPM.

It should try to avoid the use of technologies that cause issues on different containers (like CDI), and be as lightweight as possible for cloud deployment.

Initial open questions include:

• support to databases and persistence: should this be a per-container configuration or per-kjar configuration?

• can a single deployment model be used for both drools and jbpm?

• how to apply the security model from jbpm?

• does the workbench need to continue to support remote REST calls for deployments or can it be moved completely out of it?

• workbench UI consolidation for exec servers