block-read example v2.3 implementing class DlReader v2.3

- Improved algorithm for detecting connection/disconnection of the uFR devices.
- For most devices not supporting USB Host mode (without OTG) only way when attached Android Open Accessory device is plugged out from the USB port is to terminate Application by calling android.os.Process.killProcess(android.os.Process.myPid()).
- On Android devices having API 21 or higher, it is recommended to put //android:autoRemoveFromRecents="true"// in <activity> tag of the AndroidManifest.xml file.