Change image.android to use the new image.Cache class from widgets. (#2832)

* Change image.android to use the new image.Cahce class from widgets.

* fix npm scripts

* npm tsc will compile all so no need for npm run dev-tsc-tests

* fix tslint error

* image-tests use memory only cache.

* fix exception in image.android

* Change image-tests so that Image won't be GC immediately.

* Change cacheMode to enum

apps/package.json

@@ -16,6 +16,7 @@
     "tns-core-modules": "2.1.0"
   },
   "devDependencies": {
+    "tns-platform-declarations": "*",
     "babel-traverse": "6.10.4",
     "babel-types": "6.11.1",
     "babylon": "6.8.3",