redundant code in codeexecutor

Hello,

I'm developing a Henshin Concurrent Engine for gemoc with @szschaler. My code aims to reuse as much as possible of the existing concurrent engine code base. I've noticed that I had to define a Code Executor for my Henshin concurrent language extension but it's actually not doing anything as all the execution in my engine is done in the execution engine class itself.

Would it be possible to refactor the codebase so that the dependency on CodeExecutor is optional?

[Our code executor](https://github.com/eclipse/gemoc-studio-execution-moccml/blob/master/ccsljava_xdsml/plugins/org.eclipse.gemoc.execution.concurrent.ccsljavaxdsml.api/src/org/eclipse/gemoc/execution/concurrent/ccsljavaxdsml/api/dsa/executors/ICodeExecutor.java)

Thank you,
Kinga