add teamware privacy policy variables

[davidwilby]

Just making an attempt at adding these, but don't really know what I'm doing I'm afraid.

Relates to GateNLP/gate-teamware#298

[ianroberts]

I've cleaned up the template a little with my own commits, and left a couple of comments with specific questions.

Recommend we don't actually merge this PR until the teamware PR is finished, as there will be more changes to make if we want to support bind-mounting a custom policy.

[ianroberts]

I've made the change to default admin options to match host ones, but there may be an argument for making this happen in the teamware code rather than just in the chart.

[davidwilby]

I've made the change to default admin options to match host ones, but there may be an argument for making this happen in the teamware code rather than just in the chart.

This is now done in the teamware backend as well d59aae1

[ianroberts]

I've added an option to mount custom policies via a ConfigMap volume. I think this is ready to go now - if I merge this now the policies stuff won't do anything by default as the chart will still deploy the latest release (which doesn't know anything about policies), but I'll merge it anyway as you can override the image tags when installing, and I'll do another PR with the version bump once a compatible image is released.