User-friendly Validation, Improved Modules and Templating

This version adds shorthand syntax for:

• Endpoints
• Ingress
• CSI Persistent Volume

We've improved the modules system:

• Templates support path-based indexing, e.g. ${foo.things.2.x}
• Removed cumbersome exports syntax. Just write your manifest the way you normally would. (Add imports and params as needed.)

We're better than ever at helping users get their files right:

• Error messages come with the path where they originated: $.pod.containers.0.env.2
• Catch typos in your YAML field names. No more letting kubectl silently drop mistyped fields.