logging

Two things worth noting:
  1. `MaestroCascade.validate` function throws exception if jobs have the same name. This is technically backwards incompatible. I am happy to take this code out if necesary. Either way I will get rid of the TODO comment before pushing to master.
  2. I don`t want to add anything to `maestro-example` until the omnitool logger functions ready for use in maestro.