Playbill: Manage database of scheduled cultural events

This class is meant to manipulate and retrieve information about scheduled cultural events like shows, theatre exhibitions, cinema movies, etc..

The information is stored in a MySQL database.

This class provides functions for:

- Add or retrieve information about the categories of events
- Add or retrieve information about the locations where the events of a given category take place
- Add or retrieve information about the all scheduled events
- Retrieve information about the events scheduled for today or for the current week