feat(jboss): bind process engines in JNDI

- add support for binding process engines in JNDI (JBoss AS 7 only)
- the name is
  java:global/camunda-bpm-platform/process-engine/${PROCESS_ENGINE_NAME}
- The jndi name can be referenced in deployment descriptors (such as
  web.xml) or using annotations @Resource(mappedName="...")
- This creates a declarative dependency between the process engine and the
  client component (servelt context, EJB, CDI Bean...) and allows the
  Application server to manage this dependency.

related to #CAM-1008
Merge branch 'master' of github.com:camunda/camunda-bpm-platform