Auto generate various shift states alphabet keyboard automatically

If any shift state variants of alphabet keyboard layout is not
specified in KeyboardSet.Element, it will be automatically generated
from base alphabet keyboard definition.

This change also
  * Eliminates KeyboardShiftState object from Keyboard.
  * Removes various set shift state methods from Keyboard.
  * Removes KeyboardSet.Element.elementAutoGenerate attribute.
  * Separates "sticky" Key.backgroundType to "stickyOff" and "stickyOn"
  * Add preserveCase flag to smiley, .com, and labeled special keys.
  * Rename KeyboardShiftState class to AlphabetShiftState.
  * Rename some attributes from *UppercaseLetter* to *ShiftedLetterHint*.
  * Introduce shiftedLetterActivated to Key.keyLabelFlags

Change-Id: I01a0a8efeeaa76820ae728a5bdfa8d02b6ce74b7