docs: Be more explicit of the SubmitSM->DeliverSM conversion
docs: Be more explicit of the SubmitSM->DeliverSM conversion

Be clear that the database only contains DeliverSM messages and that
any SubmitSM will be convered before it is inserted.

zecke/osmo-smsc,zecke/osmo-smsc,woglinde/osmo-smsc,woglinde/osmo-smsc,zecke/osmo-smsc,woglinde/osmo-smsc