New event table:
| id | int(11) | auto_increment PK |
| description | varchar(255) | not null |
| start | date | not null |
| end | date | not null |
| organiser | int(11) | FK -> user, not null |
| uuid | varchar(36) | not null |
| participantkey | varchar(32) | not null |
| status | int(1) | not null, default 0 |
| url | varchar(1000) | not null |
New column on request: event INT(11) NULL -> FK to event table