Improve naming of the executor processes

[wouterdb]

Problem

Naming of the executors processes in the process listing and logs is not optimal

Proposed solution

1. use the name and version of all modules installed in an executor as the name of that executor

important to keep in mind

1. we want to correlate the log to the process listing
2. in the log, we can use name + PID to have something that is definitely unique.

Pointers to a solution

1. the compiler will have to export additional information, that the server will have to store and the agent pull
2. the MPPool class in the end controls the naming
3. by making the executors more aware of code/modules, the code of MPManager.get_executor can perhaps be made more elegant by moving the translation down into MPPool or MPProcess