DO NOT MERGE: Clear cache of the user dictionary when a word is added

This is a backport of  Iec2793de3fff7bf15f68f

Change-Id: If16d1c48edf084d892da722fb288e467f211b08e
Merge branch 'jb-dev' of https://android.googlesource.com/platform/packages/inputmethods/LatinIME into develop