Implement the mechanics of fxa login on android, but don't show ui fo… (#1000)

* Implement the mechanics of fxa login on android, but don't show ui for it yet. Also, scopedKeys are not yet implemented.

* Hopefully fix the package-lock conflict?

* WIP on android scoped keys

* Finish implementing login.

* created android/user.js to handle android logins

android/app/build.gradle

@@ -31,6 +31,7 @@ dependencies {
     androidTestImplementation 'com.android.support.test:runner:1.0.2'
     androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
     implementation 'com.github.delight-im:Android-AdvancedWebView:v3.0.0'
+    implementation "org.mozilla.components:service-firefox-accounts:${rootProject.ext.android_components_version}"
 }
 
 task generateAndLinkBundle(type: Exec, description: 'Generate the android.js bundle and link it into the assets directory') {