Support event family

[rmouritzen-splunk]

Related schema PR: ocsf/ocsf-schema#1260

Event classes now have an optional family attribute, allow subdividing large categories, specifically the Discovery category.

On the Categories page, when family is present, group the event classes together with family at the top with a caret, with the classes initially hidden, but shown when clicked. Consider creating an anchor for the category_uid:family tuple to allow direct linking.

On the Classes page, consider adding a Family` column. Most classes will not have anything in this column, so if this doesn't look good, leave it out or add the info somewhere else.

On the class detail page, add the family after the category. Consider adding a direct link to the category_uid:family tuple on the main Categories page.