Stunner - NewMarshallers - Variable identifiers

With the new marshallers when when we add e.g. a process variable "myProcessVar1"

the generated xml tag in the bpmn2 file looks like this:

<bpmn2:property id="var_abcd.TestProcessVariables_myProcessVar1" itemSubjectRef="_myProcessVar1Item" name="myProcessVar1"/>

See that the id is a concatenation of the variable name provided by the user in the UI with the process name (or process id). This is not necessary wrong. But personally I don't like this concatenation, since I don't know what's gonna happen if we change the process name (or process id). I don't believe we will rename all the variables identifiers if the process id changes. Probably the identifiers are recalculated each time the process is saved, but doesn't look anyway. We should also check if when the process variables are automatically injected in the scripts the name is used instead of the id.

Anyway, but this naming generates the following "problem".
When the generated process is imported by jBPM designer (something that will have to continue supporting in 7.1.GA), we see that a variable with name "var_abcd.TestProcessVariables_myProcessVar1" exists, instead of "myProcessVar1"

see attached screenshot.

I believe that we must have to use the same id calculation as jBPM old marshallers does.