add ability to do full terraform "apply" of cluster resources

[ryandeivert]

Background

Right now it's not super easy to just "apply" changes to a cluster (without doing a full build).

Steps to Reproduce

Make cluster changes, try to apply.

Desired Change

Update so we can reliably apply changes per-cluster.
Bonus: have a flag on the deploy command that will also do an "apply" at code deploy time.