Add support for installing a profile from a tag or path

[aclevername]

As part of #108 we agreed how we will implement multi-profile repos and tagging. We now need to update the controller and profile subscription to pull from these repos. We now need to update the profile subscription to match:

Version

Version (git tag) workflow:

apiVersion: weave.works/v1alpha1
kind: ProfileSubscription
metadata:
  name: foo-test
  namespace: default
spec:
  profileURL: https://github.com/weaveworks/weaveworks-profiles
  version: foo/v0.1.2

This should result in the foo directory in git tag foo/v0.1.2 being the source of truth for this profile

Branch

Branch & path base workflow:

apiVersion: weave.works/v1alpha1
kind: ProfileSubscription
metadata:
  name: bar-test
  namespace: default
spec:
  profileURL: https://github.com/weaveworks/weaveworks-profiles
  branch: main
  path: bar/

This should result in the bar directory on branch main being the source of truth for this profile