Move Kops to Submodule

[osterman]

what

• move kops to geodesic submodule (geodesic-aws-kops)

why

• So we can version it separately from geodesic

[Nuru]

@osterman How far do #439 and https://github.com/cloudposse/reference-architectures/pull/21 get you to where you want to be with respect to making kops a separate module?