Template instantiation: include mapped holes in TemplateInstance.Vars

[Tarmil]

Currently if there is a subtemplate with a ws-var:

<div ws-template="Control">
  <input ws-var="Var" />
</div>

and it is instantiated in HTML, with a mapping for the ws-var:

<div>
  <ws-Control Var="MyVar"></ws-Control>
  <button ws-onclick="Click">Click me</button>
</div>

then this var is not included in the resulting instance's Vars:

MainTemplate()
    .Click(fun e ->
        // error: The field, constructor or member 'MyVar' is not defined.
        e.Vars.MyVar.Value <- "test")

But it should be.