Set whether or not the default for a locale

This value is related to IMMS crash,
because of accessing to InputMethodInfo.isDefault() without setting the default

Change-Id: I57335c8a119ec6973ba0c42af57e597fcbb1e90f
User Dictionary error handling

* Fix the existing code to handle with duplicate dictionary entries;
* Since you can only add dictionary words if you're using this IME, warn the
  users (instead of silently failing and ending up on an inconsistent state);
* If another (unknown) error occurs while adding words, don't stay in an
  inconsistent state, and show an error message in a toast.

Change-Id: I68d971cee8789bdfbb8929b8bbaae52910c2747c