Made delete dialog an option

ControlPanel
 - delete functionality moved to deleteEntry method, delete method
 calls the dialog if the MainWindow option is selected
 
DialogWindow
 - Added a button for toggling whether the delete dialog shows up
 changed actionlistener destination to deleteEntry method
 
Lister
 - changed dialog call from delete key to call the delete method in
 control panel
 
MainWindow
 - added variable for the delete dialog option