Event Registration: Contact Dropdown

Disclaimer: This functionality only works for signed in users that have access to booking events. 

When a user is registering for an event they now get to select their contacts and do not need to input data manually(but they still can if they wish to).

A new dropdown will appear above the form:

In the dropdown the user gets to select any of their contacts that are not already registered for the selected event.

The first contact from the list is auto selected and their details fill out the form - any adjustments can be done manually or entirely new data can be given(as before). 

This supports registration for multiple tickets.