TextView - Reduces the size of the character layout.

* Character's height and advance stores the same values than size -> height and advance removed.
* Character's gradient info stores a color (Vector4) two points (Vector2) and an alpha value (float)
  These parameters are only used for some text-actors when the text is faded-out.
  A new GradientInfo structure has been added and the character only stores a pointer to that struct,
  which is NULL if is not needed.

Change-Id: Iaa09a5a384ed43722fd703ff659459196019fff9
Signed-off-by: Victor Cebollada <v.cebollada@samsung.com>