Add support for CUSTOMER ACCOUNT LOG ENTRIES on a CUSTOMER ACCOUNT

[skinkie]

#137

Needs documentation

[nick-knowles]

Currently, in Transmodel and NeTEx, CUSTOMER ACCOUNT LOG ENTRIES are linked to a CUSTOMER ACCOUNT via a FARE CONTRACT, that is a FARE CONTRACT must be created to hold the account log entries; thus a dummy FARE CONTRACT must be created for the account itself to record and log entries before any sales transactions have taken place for the account. This is not unreasonable - the account itself entails a "contract" between the customer and operator to hold and account and manage the customers details according to certain terms and conditions. . The CUSTOMER ACCOUNT LOG ENTRIES do however have a reference to the relevant account so can readily be associated with it.

If people think it really necessary, for convenience in NETEx for the purposes of data exchange, one could add a list of LOG ENTRY references also to the CUSTOMER ACCOUNT but this would be redundant from a modelling point of view

This is the current model

[nick-knowles]

Added to NeTEX UML as convenience feature. (not needed in Transmodel)