Kill dangling omc process

[AnHeuermann]

When a OMCSession isn't quit the omc process stays running forever.

Maybe finalizer is an option to kill the omc process when the memory for OMCSession is no longer accessible.

[AnHeuermann]

We can also try something similar as in OMPython: https://github.com/OpenModelica/OMPython/blob/master/OMPython/__init__.py#L167-L193

I think we shouldn't wait for quit() in OMJulia.sendExpression. Adding a timeout or a special quit function that has some timeout and would be a good idea.

[AnHeuermann]

Related to #32

[arun3688]

@AnHeuermann I guess kill(omc.omcprocess) is the better than quit as you said sometime omc process are alive even after using quit

[AnHeuermann]

I'm working on a timeout function that first tries quit() and then checks if the process is still running and kills.