Changes

[sto17-tsk51] Adds update event view, refactoring of jsf and fixes bugs
This commit adds the page updateEvent.xhtml and the managed bean 
UpdateEventController. The EventController was updated with some
refactorings (error message, navigation returns). Besides, the event
controller contains useful methods for rendering buttons. On the other
hand, all private pages were moved to private directory thus the
security constraint of web.xml can be applied automatically. For this
reason the dataset was modified with the role RegisteredUser. The other
changes in jsf pages was made to make a little more uniform the web and
to show the main links of application. Finally, some bugs in
myEvents.xhtml and EventEJB are fixed.