Require to Add new configuration for OPD Prescription auto mail.

Configuration to be sublocation wise.

Configuration Key: OPDAutoSendPrescriptionToMail
Configuration Description: Auto mail OPD prescription on OPD save.

Values: True/False.

Value function:
When True: Auto mail OPD prescription on OPD save.
When False: No auto mail OPD prescription on OPD save.
