add logback.xml to android-client, for slf4j

Author: JonasVautherin

examples/android-client/app/src/main/assets/logback.xml

@@ -0,0 +1,17 @@
+<configuration debug="true">
+  <!-- Create a logcat appender -->
+  <appender name="logcat" class="ch.qos.logback.classic.android.LogcatAppender">
+    <tagEncoder>
+      <pattern>%logger{0}</pattern>
+    </tagEncoder>
+
+    <encoder>
+      <pattern>[%thread] - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <!-- Write INFO (and higher-level) messages to logcat -->
+  <root level="TRACE">
+    <appender-ref ref="logcat" />
+  </root>
+</configuration>