Replacement of global-smtp plugin for degrowth.viper.ecobytes.net farm

To resolve #45 (closed), a plugin called global-smtp has been disabled on the degrowth.viper.ecobytes.net farm. It is suspected that it provided functionality to quickly configure all subsites at once within this WordPress multisite instance.

It is left for us to

• investigate how this affects the mail exchange of the associated sites, and
• mitigate eventually occuring side effects.