Refactor cruft from port of gcp_pilot

[thclark]

Refactor request

What is the current behavior?

To solve #52 we ported code in from gcp-pilot. which now resides in django_gcp.tasks._pilot. However, we're under a deadline for a project so do not have time to properly refactor the small subset of that code which is actually used.

Proposed Solution

We need to tidy up the code in that folder, removing most of it, and refactoring the remaining functionality to the appropriate place(s).