Allows "as <CustomType>" in parameter and return type declarations

[markwpearce]

I don't think this works yet "inside" a namespace...

[markwpearce]

I updated the PR with your comments - I also realized typings on class fields weren't being verified.. Not sure If i'm doing that correctly or not.... Namespaces are still not correctly checked though. :(

[TwitchBronBron]

@elsassph I'd appreciate your thoughts on this PR.

[elsassph]

Looking good!

[markwpearce]

This now works with namespaces!

This would be valid Brighterscript code:

Vehicles.bs:

namespace Vehicles

  class Car
  end class

  class MonsterTruck
    function driveOver(automobile as Car) as Trash.SquashedCar
      return new Trash.SquashedCar()
    end function
  end class

end namespace

Trash.bs

namespace Trash

  class SquashedCar
  end class

end namespace

[markwpearce]

@TwitchBronBron - I think everything you brought up has been addressed.