Add back personal dictionary shortcut -> word feature
AOSP removed personal dictionary shortcut -> word feature in v6. When it got merged 4,5 years ago, the feature went broke: #131 #158 (closed)
The native code for dictionary has the shortcut feature but AOSP removed that params from java side.
I've backported it from v5.1.1 https://cs.android.com/android/platform/superproject/+/android-5.1.1_r9:packages/inputmethods/LatinIME/java/src/com/android/inputmethod/latin/UserBinaryDictionary.java
Closes #131