Support import-values in chart dependencies

[fstaudt]

Following syntax in Chart.yaml should be taken into account in generated JSON schema:

apiVersion: v2
version: 1.0.0
name: bundle
dependencies:
  - name: subchart
    version: 1.0.0
    import-values:
      - child: child-key
        parent: parent-key

Properties of child-key in subchart should be considered as valid when used in parent-key in bundle chart:

# already valid
subchart:
  child-key:
    test: value
# should also be valid
parent-key:
  test: value

Short syntax for import-values in Chart.yaml should also be supported:

apiVersion: v2
version: 1.0.0
name: bundle
dependencies:
  - name: subchart
    version: 1.0.0
    import-values:
      - data

It should be treated as :

dependencies:
  - name: subchart
    version: 1.0.0
    import-values:
      - child: exports.data
        parent: data