Stop sharing EventFee::preProcess from Registration form

Stop sharing EventFee::preProcess from Registration form

Most of what this function does is silly. In particular it
sets the undeclared & not relevant _fromEmails property.

This also adds our standardised  function to
the online event forms. All event-related forms should wind up
with this public supported function (along with an approprite
mix of getParticipantID, getPriceSetID, getDiscountID

Fix undefined property on fromEmails for Participant fee