fix,feat(ProcessApplication): embedd and config

- BUGFIX: fix problem with embedded process application deployment: "default job
  executor not found". Embedded process application configured through
  processes.xml now uses DefaultjobExecutor provided by
  ProcessEngineConfigurationImpl. <job-acquisition> field in processes.xml
  file is now optional. In order to use container job executor in embedded
  deployments, corresponding MBean must be deployed manually.

- FEATURE: in order to test fix, feature for providing custom
  processes.xml file location is added by commit:

  @ProcessApplication(deploymentDescriptors={"my/location/processes.xml"})

related to #CAM-659, #CAM-678
Merge branch 'master' of github.com:camunda/camunda-bpm-platform