Logic Changes - Work In Progress

- PastMeal object is now used. The old contents of PastMeal has been
migrated to ReadPastMeal (sorry Arthur for all the confusion and lack of
communication. it seems that using an object to hold past meals is
easier and more efficient, for now)
- Entry object created - used to hold values of user input
- Updated toString methods for some classes, more useful for testing
purposes than anything
- General logic changes throughout