[NEW FEATURE]Create relation between Item and Event, Item and Place, Place and Event

[rebeccadjim]

Description of the desired solution
• Instead of manually adding which event a person was in, a relation must be created between the person and the event. Avoids having an item in multiple events.
• An item can have a localization, so a relation between place and item is necessary
• A event can have a localization, so a relation between place and event is necessary
closes #496

[create-issue-branch]

Branch feature/issue-498-_NEW_FEATURE_Create_relation_between_Item_and_Event_Item_and_Place_Place_and_Event created!