Compiler should prevent invalid scopes in query syntax

[martypitt]

When we're using scopes to narrow in a query, the compiler should detect invalid scope projections.

Here's some examples:

Types not present in scope

   type Unrelated inherits String
         model Film {
               title : FilmTitle inherits String
            }

// This is illegal, as Unrelated is not in scope.
            find { Film[] } as (unrelated:Unrelated) -> {
               title : FilmTitle
            }[]

Types amgibuously referenced in array

            type ActorName inherits String
            model Movie {
                title : MovieTitle inherits String
                actors : ActorName[]
            }
         """.compiledWithQueryProducingCompilationException(
            """
                // This should be illegal, as ActorName is actually present in an Array,
                // (ActorName[])
                // so the projection scope is ambiguous.
                //
            find { Movie } as (actors:ActorName) -> {
               actorNames : ActorName
            }