engine: Corrections to Event.equal to avoid confusions and unexpected behaviors.

- Changed the covariant version of the Event.equals(Event other) to
override standard java Object.equals(Object other), the equality is
a natural identity and is based on the privateName & privateOwnerType
properties.

- Generated a hashCode() method which is compatible with the equals
implementation.

- Renamed Event.equals(EventDefinition ed) to
Event.matchesDefinition(EventDefinition ed) as the name of the method
overloads java standard Object.equals(Object other) method which is
risky and may cause unexpected behaviors.

Change-Id: Idca42d6a61454162db412429e55898f15152c12d
Signed-off-by: Asaf Shakarchi <asaf@redhat.com>