Changes

Solves several problems with the tests
The event creation form includes a calendar component for selecting the
event date that was causing test execution blocks. This commit hides
this component by using a little trick (clicking in a previous component
and waiting a few milliseconds).
In addition, the usage of beans.xml and TestPrincipal in 
JoinEventControllerTest was causing an unexpected behaviour, as the
Principal didn't returned "anonymous" when no user where logged. This
test case also had several implementation errors and the LoginPage
class, on which this test case depends, where inconsistent with the HTML
content of the login.xhtml page.
Finally, the EventsDatset has been refactorized to remove several unused 
methods and to add the id to the events.
Despite this changes, there are several elements of this classes that
can be improved.