[IM] Allow peering manager test mode via application.ini

Introduces two new applicaton.ini parameters:

peeringmanager.testmode = false
peeringmanager.testemail = "user@example.com"

;; The Peering Manager allows your members to send peering requests to other members
;; that contain all the necessary peering details.
;;
;; For testing / experimentation you can enabled test mode below and, when enabled, all
;; peering requests will be send to the testemail.
;;
;; NB: This does not apply to any BCC emails you add. The CC recipient in the request
;; dialog will be ignored in test mode.
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