Rewrite of Remote Smart Card Reader

- use material design
- use AsyncTask instead of Runnable for VPCDWorker to integrate with the
  App's lifecycle
- use a dedicated Preference Activity
- integrated zxing's QR code scanner
- use Snackbar instead of Toast
- capture debug messages in log instead of explicitly passing messages
- use reader mode only, breaks support of Android before kitkat

remote-reader/app/src/main/res/layout/content_main.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<android.support.v4.widget.NestedScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    app:layout_behavior="@string/appbar_scrolling_view_behavior"
+    tools:context="com.vsmartcard.remotesmartcardreader.app.MainActivity"
+    tools:showIn="@layout/activity_main">
+
+    <fragment
+    xmlns:android="http://schemas.android.com/apk/res/android"
+        android:name="com.vsmartcard.remotesmartcardreader.app.remotesmartcardreader.MyLogFragment"
+        android:id="@+id/log_fragment"
+        android:layout_margin="@dimen/text_margin"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+</android.support.v4.widget.NestedScrollView>