Added state (i.e. undo or redo) and identifier to BaseHistoryItem.
Added state (i.e. undo or redo) and identifier to BaseHistoryItem.

jakeclawson/Pinta,Fenex/Pinta,PintaProject/Pinta,PintaProject/Pinta,Fenex/Pinta,jakeclawson/Pinta,Mailaender/Pinta,Mailaender/Pinta,xxgreg/Pinta,PintaProject/Pinta