No more ambient modules for tns-core-modules/* subpackages.

- Use path mappings in tsconfig.json to resolve module typings
- Only use ambient mobules for global API's
- Move single-file modules to a subdir with the same name so that
we can provide a hand-written typing next to it (via package.json)
- Delete all mentions of tns-core-modules.d.ts
- Delete reference d.ts assembly build steps. Not needed anymore.
- HACK! Use a <reference> for global typings in application.d.ts
to avoid publishing a separate @types/tns-core-modules package.
- Rename declarations.d.ts to tns-core-modules.d.ts to preserve
JS project mappings in references.d.ts (the only place we use those)

tns-core-modules/ui/layouts/stack-layout/package.json

@@ -1,2 +1,5 @@
-{ "name" : "stack-layout",
-  "main" : "stack-layout" }
+{
+  "name" : "stack-layout",
+  "main" : "stack-layout",
+  "types" : "stack-layout.d.ts"
+}

tns-core-modules/ui/layouts/stack-layout/stack-layout.d.ts

@@ -1,19 +1,17 @@
-declare module "ui/layouts/stack-layout" {
-    import { LayoutBase, Property } from "ui/layouts/layout-base";
+import { LayoutBase, Property } from "ui/layouts/layout-base";
 
+/**
+ * A Layout that arranges its children horizontally or vertically. The direction can be set by orientation property.
+ */
+export class StackLayout extends LayoutBase {
     /**
-     * A Layout that arranges its children horizontally or vertically. The direction can be set by orientation property.
+     * Gets or sets if layout should be horizontal or vertical.
+     * The default value is vertical.
      */
-    class StackLayout extends LayoutBase {
-        /**
-         * Gets or sets if layout should be horizontal or vertical.
-         * The default value is vertical.
-         */
-        orientation: "horizontal" | "vertical";
-    }
+    orientation: "horizontal" | "vertical";
+}
 
-    /**
-     * Represents the observable property backing the orientation property of each StackLayout instance.
-     */
-    export const orientationProperty: Property<StackLayout, "horizontal" | "vertical">;
-}
+/**
+ * Represents the observable property backing the orientation property of each StackLayout instance.
+ */
+export const orientationProperty: Property<StackLayout, "horizontal" | "vertical">;