Create TextServiceManager and SpellCheckerService

Bug: 4176026

Spec of TextServiceManager
- Chooses the most applicable TextService(e.g. SpellCheckerService, WordBreakIteratorService..)
    for each locale

Spec of SpellCheckerService
- Returns whether the given string is a correct word or not
- Returns Suggestions for the given string

Change-Id: Ia25e7b4f308778891929e31b8cbd741f6848cce4