added support for namemaps on control properties

[mizrael]

added new PropertiesNameMaps property on the ControlInstance class

Screens:
  Screen1:
    Children:
      - Dropdown1:
          Control: Classic/DropDown
          Properties:
            Items: |-
              =[{Id: 1, Title: "Item 1", Desc: "desc1"}, {Id: 2, Title: "Item 2", Desc: "desc2"}, {Id: 3, Title: "Item 3", Desc: "desc3"}]
            X: =246
            Y: =420
          PropertiesNameMaps:
            Items:
              Value: Title

[joem-msft]

I'd hold off on getting the schema for this approved first. but my comments are relevant none theless.

[joem-msft]

another proposal would be to just use NameMaps, we can probably elide the 'Properties' prefix. But lets wait for a review on the schema before changing the code.

[mizrael]

PropertiesNameMaps makes it clear that we're referring to additional metadata to enrich existing properties

[joem-msft]

Open this file in VS Code. You'll see there are some squigglies due to this property not existing in the schema.
Whenever changing the schema, we should update the schema file here: src\schemas\pa-yaml\v3.0\pa.schema.yaml

I can talk with you offline how best to test changes in your inner-dev-loop.

After updating that file sufficiently, then you run src\schemas\publish.cmd so it compiles and updates the final file at schemas\pa-yaml\v3.0\pa.schema.yaml.

[mizrael]

abandoning this PR, we have agreed on moving forward with a different schema to represent name maps:

- MyControl
    Control: Chart
    Properties:
      Items: |-
        =[{Id: 1, Title: "Item 1", Desc: "desc1"},
          {Id: 2, Title: "Item 2", Desc: "desc2"}]
      Items.Label: =Title
      Items.Series1: =Val1
      Items.Series2: =Val2
      Items.Series3: =Val1