Feature/program page control import

Per [story 57529526](https://www.pivotaltracker.com/story/show/57529526).

- New view function to handle control->program import (existing ones assumed directive).
- Generalize `ControlConverter` to allow for possibility of attaching to Program.
- New templates for Control/Program interface (mostly copied from control/directive import).
- Generalize control-import template to cover importing to programs (rather than create a new function).