Added paymentTransactions() to CommissionJunction.php

+ Added private attribute to the class: $_accountId as it is needed in order to request the reports to CJ

+ Added a few lines to get the $_accountId from the cookie, I used the checkConnection() function for this as I can see the same is being done to get $_memberId

+ Added function paymentTransactions(): 

    1. It checks the period for the current invoice (end date: date of the current invoice, end date: date of the previous invoice)

    2. It gets the ids of the payments for each merchant for the current invoice

    3. It extracts the transactions associated to the merchant payment id for the current invoice