Create TextServiceManager and SpellCheckerService

Bug: 4176026

This CL inherits https://android-git.corp.google.com/g/112600

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: Iaa425c7915fe70767ad0b17bf6c6fbcd2a1200b2