Move add/removeInteraction into wm.contact

WorldManager has now an object called contact.
In this object, there are several methods regarding contacts.

addInteraction and removeInteraction have been merged and moved in
contact:
wm.contact.showContacts(list_of_body_name_pair, display)

removeAllInteractions has been moved in:
wm.contact.hideAllContacts()
Move wm.createOConnectorContactBody to wm.contact.createOConnectorContactBody