Implement tagging in pipeline and pipeline-templates

[boscard]

Implement tagging in pipeline and pipeline-templates.
This will allow us to test multiple versions of pipelines on one Spinnaker instance.
https://www.spinnaker.io/guides/user/tagging/

[kacpersaw]

To save or to get pipelines with tag, you need to add tag param to URL.

Floodgate needs to be rewritten so that it can save a specific resource (with tag).
E.g.

floodgate sync --application xyz --tag my-awesome-tag