Bug 844717 - Add Thai input method for Gaia

I've just added Thai input method. The screenshot is attached. 

An additional row is added because Thai has a lot of glyphs and cannot fit them all in 4 rows layout. 

![ 2013-02-25 14 36 24 ](https://f.cloud.github.com/assets/178924/190943/243460fc-7f1e-11e2-881b-cbd77a25c359.png)
![ 2013-02-25 14 36 29 ](https://f.cloud.github.com/assets/178924/190942/242f67c8-7f1e-11e2-8d02-49447eb8a29a.png)
![ 2013-02-25 14 36 36 ](https://f.cloud.github.com/assets/178924/190941/2372ac8c-7f1e-11e2-8998-c967d1458191.png)