pre-release execution functionality in separate api

Apologies for the monster pull request.

This contains execution functionality in a separate `maestro.api.exec` module. This is not yet intended to be used by users, and we may make backwards incompatible changes at any time.

Known issues in this early version of the execution work:
  1. The `viewHive` zip bug
  2. Missing documentation
  3. Missing stats for the query executions
  4. Missing sqoop execution trait
  5. Use of dummy configurations for upload instead of taking the configuration for the execution
  6. Methods in the Miscellaneous module free to a good home
  7. `ViewExecutionSpec` using a custom matcher that should exist in thermometer
  8. The framework around running the execution is not done yet
  9. The framework around configuring executions, if that is what we want, is not done yet
It is related, actually, although it could easily have been done in a less invasive way. But now that I am returning the list of files uploaded, it became quite a bit nicer to separate the list of control files from the list of data files. And than that change naturally percolated down. I could easily have avoided percolating changes down, but I thought all the methods I touched became quite a bit simpler as a result.