Refactor on UserHistoryDictionary

java/src/com/android/inputmethod/latin/BinaryDictionary.java

java/src/com/android/inputmethod/latin/Constants.java

...android/inputmethod/latin/ExpandableBinaryDictionary.java

...c/com/android/inputmethod/latin/ExpandableDictionary.java

java/src/com/android/inputmethod/latin/LastComposedWord.java

java/src/com/android/inputmethod/latin/LatinIME.java

...rc/com/android/inputmethod/latin/RichInputConnection.java

java/src/com/android/inputmethod/latin/Suggest.java

java/src/com/android/inputmethod/latin/WordComposer.java

...android/inputmethod/latin/makedict/BinaryDictIOUtils.java

...rc/com/android/inputmethod/latin/makedict/FormatSpec.java

.../android/inputmethod/latin/makedict/FusionDictionary.java

...utmethod/latin/personalization/UserHistoryDictionary.java

...atin/personalization/UserHistoryDictionaryBigramList.java

...droid/inputmethod/latin/utils/UserHistoryDictIOUtils.java

...hod/latin/personalization/UserHistoryDictionaryTests.java

.../inputmethod/latin/utils/UserHistoryDictIOUtilsTests.java