Allow Multiple Payee Numbers in User Settings

For Locums, when they bill they need to bill under the payee # of the doctor they are covering. Currently, MYLE only allows 1 payee number to be inputted in the user's settings, which does not support locums who cover multiple doctors in short timespans.

MD Billing allows multiple payee numbers and receives the default payee number directly from MYLE. Therefore, if MYLE allowed multiple payee numbers, this information could be sent to MD Billing.