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/build.gradle

@@ -5,7 +5,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:1.3.0'
+        classpath 'com.android.tools.build:gradle:1.5.0'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
@@ -17,3 +17,7 @@ allprojects {
         jcenter()
     }
 }
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}