When throwing a BpmnError it would be cool if we could also specify a cause.

This has two advantages:

1. The cause details are automatically included into the message text
2. When a BpmnError is thrown as a reaction on an application exception, from the catch block for the exception, sonar qube will not complain about the original exception not being logged or rethrown.

I've created a patch for that: https://github.com/camunda/camunda-bpm-platform/pull/776