Allow exceptions to namespace injection

[haines]

As a:
component author using a third-party Helm chart

I want:
to inject namespaces into all resources in the chart, except those that don't support them

So that:
I can use a third-party chart that doesn't have parameterised resource namespaces, without getting a diff between my manifests in git and the state of the cluster because the manifests have namespaces injected into resources that don't support them.

Describe the solution you'd like:
Extend the injectNamespace option to allow either a boolean (maintaining current behaviour) or something like

injectNamespace:
  except:
    - kind: ClusterRole
    - kind: ClusterRoleBinding  

I'm not sure what should be required/allowed to specify the exceptions:

• just kind?
• apiVersion and kind?
• an arbitrary map to enable matching on any field? (seems overkill)

Describe alternatives you've considered:
Build a list of resources that don't support namespaces into Fabrikate - seems like this would be likely to fall short for custom resources and would be a maintenance burden

Additional context:
Original motivation: #102
It doesn't look like Helm is going to support namespace injection any time soon: helm/helm#3553 (comment)