Implemented the enter and delete keys when selecting events

When enter or delete is pressed after selecting an event from the 
list a dialog window will appear to make changes/confirm delete

ControlPanel
 - added constructor for quick duplication to appear in dialog window
 - added get/set methods for the necessary variables
 - moved add and remove function to new methods from the actionListener
 
MainWindow
 - send a reference of itself to the Lister when creating it
 
Lister
 - Created behavior for the enter and delete keys in keylistener
 
Dialog window
 - will handle the creation of pop up windows that require interaction