Clearer toString message with parameters of event

services/src/main/java/ch/hepia/event/Event.java

...ces/src/main/java/ch/hepia/event/EventAccountCreated.java

...es/src/main/java/ch/hepia/event/EventAccountCredited.java

...src/main/java/ch/hepia/event/EventAccountDoesntExist.java

...src/main/java/ch/hepia/event/EventAddProductQuantity.java

...ices/src/main/java/ch/hepia/event/EventCreateAccount.java

...ices/src/main/java/ch/hepia/event/EventCreateProduct.java

...ces/src/main/java/ch/hepia/event/EventCreditAccepted.java

...es/src/main/java/ch/hepia/event/EventCreditAnAccount.java

...ices/src/main/java/ch/hepia/event/EventCreditRefused.java

...es/src/main/java/ch/hepia/event/EventCreditWithdrawn.java

...ces/src/main/java/ch/hepia/event/EventOrderCancelled.java

services/src/main/java/ch/hepia/event/EventOrderCreated.java

services/src/main/java/ch/hepia/event/EventOrderPlaced.java

...ices/src/main/java/ch/hepia/event/EventOrderPrepared.java

services/src/main/java/ch/hepia/event/EventOrderSent.java

...ces/src/main/java/ch/hepia/event/EventProductCreated.java

...src/main/java/ch/hepia/event/EventProductDoesntExist.java

.../src/main/java/ch/hepia/event/EventProductOutOfStock.java

...c/main/java/ch/hepia/event/EventProductQuantityAdded.java