Initial Package Design

[FrankD412]

This issue covers the initial pyaestro package layout and the interfaces that it should cover.

So far, the proposed top level package layout is as follows.

abstracts
interfaces
|--mpi
    |--MpiFactory
    |--srun
    |--jsrun
    |--openMPI
|--scheduling
structures
|--graphs
    |--Graph (abstract)
    |--MultiGraph