Flux release 1.4.2

This release includes a number of usability improvements, the majority
of which were suggested or contributed by community members. Thanks
everyone!

Fixes

• Don't output fluxd usage text twice
  weaveworks/flux#1183
• Allow dots in resource IDs; e.g., default:deployment/foo.db, which
  is closer to what Kubernetes allows
  weaveworks/flux#1197
• Log more about why git mirroring fails
  weaveworks/flux#1171

Improvements

• Interpret FluxHelmRelease resources that specify multiple images to
  use in a chart
  weaveworks/flux#1175
  (and several PRs that can be tracked down from there)
• Add an experimental flag for restricting the view fluxd has of the
  cluster, reducing Kubernetes API usage: --k8s-namespace-whitelist
  weaveworks/flux#1184
• Share more image layers between quay.io/weaveworks/flux and
  quay.io/weaveworks/helm-operator images
  weaveworks/flux#1192
• Apply resources in "dependency order" so that e.g., namespaces are
  created before things in the namespaces
  weaveworks/flux#1117