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)

tsconfig.shared.json

@@ -15,6 +15,13 @@
         "reactNamespace": "UIBuilder",
         "lib": [
             "es6", "dom"
-        ]
+        ],
+        "baseUrl": ".",
+        "paths": {
+            "*": [
+                "./tns-core-modules/*",
+                "./node_modules/*"
+            ]
+        }
     }
 }