Use SlidingUpPanelLayout for emoji.

PS2:
Populate the emoji view with either smileys or emojis
depending on the user settings.
Re-init the emoji view in the vertical sliding panel
in onResmue() to reflect possible changes the user may
have made in settings.

Change-Id: Id9f6d3846efb10fe215ed3ab0dc4e89a212bc681