Be able to get all process variables injected as a payload map, even if the explicit injection of a named variable is used.

### Scenario

* Library version: 0.0.4

### Current Behaviour

If you use `@Variable` only those variables are fetched from the payload and will be given to you. If you in addition inject the Payload `Map` as a parameter it will still only contain the variables present as individual method parameters.

### Wanted Behaviour

Be able to overwrite this behavior with additional attribute of the `ProcessEngineWorker` annotation and still fetch all variables. (adding `overwriteVariableFetching` boolean parameter)

### Possible Workarounds

Not use `@Variable` and `Map` in the same method.