Install docs are very Serving focused.

[mattmoor]

This came up in TGIK8s talking about Knative.

1. We should show how to install just Build
2. We should clarify that Istio is a Serving/Eventing dependency, but not a Build dependency
3. We should clarify that Serving bundles Build (for now).
4. We should install release-no-mon.yaml by default, and talk about installing monitoring separately.
5. We should add a section on installing eventing.

[RichieEscarez]

1 and 3 were recently completed

[samodell]

This work is in progress: #542 and to some extent #565