new CmdGoToBaseScreen (acts like a 'return'). allows edit, mark, delete, clear overdue to go to base screen.  fixed major bug btw parsing EDIT_FIELD and EDIT_ITEM.
clear all overdue is ready (from overdue screen). able to go back to VIEW_LAST_SEARCH screen (analagous to going to base screen: search). able to go back to view overdue screen.
Merge branch 'master' of https://github.com/cs2103aug2014-t14-3c/main