Fix callback order issue, memory leak issue in GenItem,GenItemClass

Fix callback order issue, memory leak issue in GenItem,GenItemClass

 - GenItemClass::DeleteHandler was called, after related item was cleanup
   So, developer can't access to related item in DeleteHandler.
   I change the source of DeleteHandler
 - Memory leak on ItemObject
   s_IdToItemTable and s_HandleToItemTable was not removed when Item was deleted, So ItemObject can't released.

Change-Id: Ibe5ada852f1c1d777ece5667b3aafa5be4cf119d