ENH : Added Korean to HelloWorld
API : added available to ToolBase

Same logic as with BaseDataHandler, should provide tools a way to report
and run-time if they are usable
API : change BaseDataHandler.metadata return value to dict()

 - return empty dict so that the base function at operate as
   the base of a super() chain
API : tweaked ImageSource required functions a bit

  - still sorting out the best way to design this
RFCT : refactored where logic lives if FileHandler family

 Pushed most of the logic up to the base-class
ENH : Added basic ImageSource implementation

 - uses scipy.misc.imread
EXMP : Added example tool to exercise new ImageSource