Mobile app initial implementation.

Closes #3 (closed)

android/app/src/main/AndroidManifest.xml

+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    package="com.vereign.app">
+
+    <uses-permission android:name="android.permission.INTERNET" />
+
+    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
+         calls FlutterMain.startInitialization(this); in its onCreate method.
+         In most cases you can leave this as-is, but you if you want to provide
+         additional functionality it is fine to subclass or reimplement
+         FlutterApplication and put your custom class here. -->
+    <application
+        android:name="io.flutter.app.FlutterApplication"
+        android:label="${appLabel}"
+        android:icon="@mipmap/ic_launcher">
+        <activity
+            android:name=".MainActivity"
+            android:launchMode="singleTask"
+            android:theme="@style/LaunchTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize">
+            <!-- This keeps the window background of the activity showing
+                 until Flutter renders its first frame. It can be removed if
+                 there is no splash screen (such as the default splash screen
+                 defined in @style/LaunchTheme). -->
+            <meta-data
+                android:name="io.flutter.app.android.SplashScreenUntilFirstFrame"
+                android:value="true" />
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.LAUNCHER"/>
+                <data
+                    android:scheme="app"
+                    android:host="com.vereign.app" />
+            </intent-filter>
+        </activity>
+
+        <activity
+            android:name="net.openid.appauth.RedirectUriReceiverActivity"
+            tools:node="replace">
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+
+                <data
+                    android:scheme="app"
+                    android:host="com.vereign.app"
+                    android:path="/oauth2"/>
+            </intent-filter>
+        </activity>
+
+        <activity
+            android:name="github.showang.flutterappauthwrapper.OAuthActivity"
+            android:configChanges="orientation|screenSize"
+            android:theme="@style/Theme.AppCompat.Translucent" />
+    </application>
+</manifest>