Populate jitenshea.tasks.controller.py with queries contained in some luigi.Task run() methods

[delhomer]

PR #36 has introduced a lighter and clearer way of querying database when running a standard Luigi Task. The code smartness is then moved to a controller.py module, instead of being in Luigi task run() methods.
In a similar fashion than for prediction, database queries in regular tasks should be moved to this new module.