Merge English bigram dictionary to the sandbox: https://android-git.corp.google.com/g/#change,56796

Change-Id: I35a576ec3e32187c508aca7ed9392b77ae5fade4
tree: e0aefa4b86ece9daceb3860e773731d07727aa3a
  1. dictionaries/
  2. java/
  3. native/
  4. tests/
  5. Android.mk
  6. CleanSpec.mk