Deployer

Adds a deployer component, which uses the queue (#547) to schedule deployments using different strategies (currently one-by-one or all-at-once).

Resolves #602.
It's already been scaled down to zero in the for loop, so deleting it here doesn't really do anything.

The original code deleted it to have the same effect as scaling to zero, and also used the fact there was only one formation per app to determine which formation to scale, which we don't need to do anymore.