Use Angular CLI instead of ngm for building

Some commands:

npm run build      - to build the library.  Output is in dist/ng2-file-upload/.
npm run test       - to run tests.  Coverage report is in coverage/ as before.
npm run demo.serve - to build demo application and serve it through browsersync
npm run start      - to run demo application using `ng serve`.  Requires the library to be built and linked first.

src/ng-package.json

@@ -0,0 +1,7 @@
+{
+  "$schema": "../node_modules/ng-packagr/ng-package.schema.json",
+  "dest": "../dist/ng2-file-upload",
+  "lib": {
+    "entryFile": "index.ts"
+  }
+}