Default config ExternalUrl is always http

[Beyley]

https://github.com/LittleBigRefresh/Bunkum/blob/3d635e3b0d58ed601f9e8985ef9c92ddf0aa66a9/Bunkum.Core/Configuration/BunkumConfig.cs#L20
It should default to the protocol in use

[jvyden]

Can probably be solved by just passing the protocol name straight into the constructor of BunkumConfig