Add config support for screepsmod-mail-aws-ses

[JakeLoustone]

It was suggested on the Screeps Discord channel that configuration support for https://github.com/ScreepsMods/screepsmod-mail-aws-ses be added to screepsmod-admin-utils, so that you would not have to fork screepsmod-mail-aws-ses to change the the from user to something you have whitelisted in your aws account.