Change from "classic" TS 1.6 imports to the default resolution scheme.

- Use relative imports in place of most of our absolute ones.
- Add "private" ambient modules for modules that we need to import using
an absolute path (e.g. when app/.../test-something.ts needs to import
ui/styling/style-scope)

ui/layouts/stack-layout/stack-layout.ios.ts

@@ -1,7 +1,7 @@
 import utils = require("utils/utils");
 import enums = require("ui/enums");
 import view = require("ui/core/view");
-import common = require("ui/layouts/stack-layout/stack-layout-common");
+import common = require("./stack-layout-common");
 
 global.moduleMerge(common, exports);
 
@@ -182,4 +182,4 @@ export class StackLayout extends common.StackLayout {
             childLeft += childWidth;
         }
     }
-}
+}