tilt up --labels

[nicks]

Current Behavior

We now have tilt enable --labels=fe, which lets you start up all the services that have this label.

But tilt up does not have a way to select services by label.

Describe the Feature You Want

tilt up --labels=fe should start up only the services that match the label

Why Do You Want This?

Parity with the tilt enable CLI, allowing people to choose which services to start with.