Cleanup the runtime mess

Try to make a proposition to cleanup the runtime interface.

Based on what @reazulhoque needs for PaRSEC DTD, the need to fix the flushes, and the need to move to asynchronous acquire callbacks. I suggest we clean up the RUNTIME interface to do that.

Here is a proposition of interface, that does not include the profiling and the options yet.

I'm waiting for feedbacks from @all