Naive scheduler

[fjosw]

I implemented an alternative scheduler which I call "naive". All it does is schedule modules in the order they are created. I need this feature for workflows with many WilsonClover type actions. As the Clover term is calculated in the constructor of the action the genetic scheduling for this kind of applications can exceed wall clock time. I think also @rrhodgson has applications where this kind of scheduling is needed.

The alternative scheduler can be chosen via the following addition to the xml global header

<scheduler>
    <schedulerType>naive</schedulerType>
</scheduler>

If no scheduler is specified Hadrons defaults to the genetic algorithm but raises a warning.

For a more consistent naming one could consider renaming schedule into geneticSchedule.

[aportelli]

Looks great, many thanks!