Awing WebDAV + HttpActionController patch

Adds:
  - com/airhttp/HttpRequest.as
  - com/airhttp/HttpResponse.as
  - com/airhttp/HttpActionController.as
  - com/airhttp/WebDavController.as

Updates:
  - com/airhttp/HttpServer.as

How to enable WebDAV drive endpoint:
  In your app startup where you create HttpServer, register:
    webserv.registerHttpController(new WebDavController("/dav", "c:\\___Fire\\Bin\\Tree"));

  Then map drive in Windows to:
    http://localhost:4567/dav

Notes:
  - Supports OPTIONS, PROPFIND (Depth 0/1), GET, PUT, DELETE, MKCOL.
  - Intended for internal usage (HTTP on localhost), not hardened for internet exposure.