Package Tesseract training data with apk, unpack into fs cache

* For tesseract to work on phones without special preparation of
  placing the tesseract training data on the SD card, we needed to
  package the training data files (file in this case) with the APK.
* eng.traineddata is now stored in the assets of the APK, and there
  is a concurrent task that unpacks it when a DataReceive intent with
  image is received by the activity.  Tesseract is then initialized
  with the unpacked directory containing the training data.