Lab3 initiation - Githubissues

Did some fixes, which are required for the next step - third task. Things I did:

Moved GUI drafts and user-system interaction sequences to the user interface requirements,
Created a more detailed sequence diagram for the calendar Use Case.
Altered the class diagram: changed some relations, added classes.
Standardized images naming. GUI images start with "GUI", user-system interaction sequence diagrams with "SEQ", detailed design sequence diagrams "DSEQ", robustness diagrams - "RD".
Fixed user stories a bit.

Tristanas / PSI2-Food-Bee-Inc