Trigger bpmn error

[martin-grofcik]

Description: When triggerable service task throws BpmnError during the trigger execution, the exception is not handled by any event subprocess.

Expected behavior When BpmnError is thrown in the trigger method of the triggerable service task, any event subprocess can handle error.

Code https://github.com/martin-grofcik/flowable-engine/commit/27d6f23d422c0c728546f36c9b86465915baf56f https://github.com/martin-grofcik/flowable-engine/tree/%233094_triggerableBpmnError

The proposed solution (jUnit test covers only one case) is to add try/catch blocks to all trigger calls.

[martin-grofcik]

@tijsrademakers, @jbarrez : What is your opinion? I can contribute with the fix for all cases.

[tijsrademakers]

@martin-grofcik , if this doesn't work right now for handling the BpmnError in event sub processes then it's a bug and good to fix.