Added Serialization to this class (nothing to do, but add the interface).  Allows us to use the EmptyIcon with SwingX serializable classes like JXTable.
Added Serialization to this class (nothing to do, but add the interface).  Allows us to use the EmptyIcon with SwingX serializable classes like JXTable.

RockManJoe64/swingx,RockManJoe64/swingx