Remove unnecessary casts

Gson used to deserialize numerical values as Double so that ugly casts were necessary
in some places. After the migration to Jackson, these casts can be removed.

Refs #955
Fix ClassCastException in NotificationTypeFactory

The "fault_count" attribute of a Notification is always an integer, so
casting it to a double and then rounding it is neither necessary nor does
it work.

Fixes #955