Changes

tsk29-32 Refactors Event and completes EventTest
Event entity has been completely refactored, deleting the only
bidirectional relationship with the User in the User side and keeping
only the Event side. Names and types of some fields have also been
changed, and JPA converters and XML Adapters (for JSON serialization)
have been created where required. EventTest has been completed, using a
new EventParameters util class.
As this causes lots of  breaking changes, all the upper layers and
datasets had to also be updated, including the SQL creation scripts.