Build embedded Parity JS properly and separatly (#4426)

* Add a specific embed webpack build // output assets in JSON

* WIP Embed

* Updated Webpack

* Update exports // Webpack config

* Fix app build fail

* Fix NPm scripts

* Reduce Embed dependencies

* Fix NPM exports

* remvoe stats

* Lazy-Load worker (not to load in embed)

* PR Grumbles + Fix tests

js/src/util/signer.js

@@ -15,7 +15,7 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 import scrypt from 'scryptsy';
-import * as Transaction from 'ethereumjs-tx';
+import Transaction from 'ethereumjs-tx';
 import { pbkdf2Sync } from 'crypto';
 import { createDecipheriv } from 'browserify-aes';