Refactor basic reduction

[kbwestfall]

As titled.

This PR does a number of things:

• Updates some of the basic infrastructure for the name change
• Introduces classes to handle the difference between the new and old camera (the new camera is still not in regular operation yet!)
• Makes some significant changes to the workflow for the basic reductions. Much of this is superficial, but there are some changes to, e.g., when the cosmic-rays are detected and some details with the field-flattening.

Importantly, this requires some changes to ccdproc that I'm going to issue a PR for next.

[kbwestfall]

For the ccdproc change, see astropy/ccdproc#873