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/utils/lazy.d.ts

@@ -1,8 +1,6 @@
-declare module "utils/lazy" {
-    /**
-     * A function that evaluates the action only once.
-     * @param action The action to be evaluated to get the result.
-     * Returns the evaluated result.
-     */
-    export default function lazy<T>(action: () => T): () => T;
-}
+/**
+ * A function that evaluates the action only once.
+ * @param action The action to be evaluated to get the result.
+ * Returns the evaluated result.
+ */
+export default function lazy<T>(action: () => T): () => T;