Redesign login page. Add OAuth2 support.

android/app/src/main/AndroidManifest.xml

@@ -44,6 +44,16 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+
+        <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" >
+            <intent-filter android:label="flutter_web_auth">
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="org.thingsboard.app.auth" />
+            </intent-filter>
+        </activity>
+
         <!-- Don't delete the meta-data below.
              This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
         <meta-data