Ambari via Jsonnet

Jsonnet input manifests to a struct containing a field "resources" which is assumed to be a list of cloud resources to deploy. 2 Examples are provided:

ambari.jsonnet (matches existing Ambari examples)

ambari_small.jsonnet (a variant of ambari.jsonnet which overrides the instances size (ram/cores) and reduces the number of agents).
If you're going to remove this (which is fine), please also remove the `Error` and `JsonnetNotFoundError` classes above.