Reorganize settings in Google Keyboard

Changes :
Input languages ->  Languages
Input preferences -> Preferences
Multi lingual Options -> Multilingual Options
Keyboard Theme -> Theme
Gesture typing preferences -> Gesture typing

**New
 Appearance
        -> Theme
        -> Custom input style

**Removed
 Multilingual options from L dynamically

Bug: 11866784
Change-Id: I07404c27868e1b087b0cafb63d2031a5b493a885