Help updates for echolist config section

The "EchoLists" help menu only worked when you first enter the sub-menu and would get wiped out by subsequent child-menu help text.

Filled out the "Configuring an EchoList" help text.

Fixed issue seen where deleting an EchoList's Required Key didn't set the "dirty config" flag, so saving of changes was not prompted when exiting (if that was the only change made).