Fix Resources Management View:
Hide "Quantity" when update view
When group is updated, its option in  group selector (<select name="group">) is also updated
Added javax.persistence.PersistenceException as Exception to Handle
Some tags fixed
Manual execution of onload methods when html is manually changed by $.load() jQuery function, because scripts loaded with that function aren't automatically executed
Fix: remove 'g' prefix from resource's id group. It has to be a string that Java can cast into number
Fix on SQL queries of reservations between dates. Checks about the border dates (start and end) was wrong because sometimes there were 'equals' when it shouln't.