This change introduces:

* New KeyboardView attribute
  * keyLargeLetterRatio to specify large letter text size.
  * keyHintLabelRatio to specify hint label text size.
  * keyHintLabelColor to specify hint label text color.
  * keyPreviewTextRatio to specify key preview text size.
* New Key.keyLabelOption flags
  * alignLeftOfCenter, align the key label slightly left of the key center.
  * largeLetter, use keyLargeLetterRatio to draw key letter.
  * hasHintLabel, draw keyHintLabel at the right of key letter.
  * followKeyHintLabelRatio, draw the key label following keyHintLabelRatio size.
* Renames
  * Key.keyHintLetter to keyHintLabel.
  * Key.keylLabelOption fontFixedWidth to fontMonoSpace.
  * Key.keylLabelOption popupHint to hasPopupHint.
* Removes
  * number icon releted attributes and declarations.

Change-Id: I2f456737e3a46209e5f48b5155951b2b21a33859