`Set-ACMEProxy` appear to be not functionnal.

[XSBen]

Hi,

When I set proxy with Set-ACMEProxy:
Set-ACMEProxy -UseProxy 'https://*proxy*:8080

New-ACMEIdentifier -Dns "test.test.fr" -Alias test
New-ACMEIdentifier : Impossible de se connecter au serveur distant
Au caractère Ligne:1 : 1
+ New-ACMEIdentifier -Dns "test.test.fr" -Alias test
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [New-ACMEIdentifier], WebException
    + FullyQualifiedErrorId : System.Net.WebException,ACMESharp.POSH.NewIdentifier

If I set same Proxy in Internet Explorer, it's ok:

New-ACMEIdentifier -Dns "test.test.fr" -Alias test

IdentifierPart : ACMESharp.Messages.IdentifierPart
IdentifierType : dns
Identifier     : test.test.fr
Uri            : https://acme-v01.api.letsencrypt.org/acme/authz/qjUJweDLZWSv2hRGPEp1KVADeO
Status         : pending
Expires        : 02/05/2018 06:17:59
Challenges     : {, }
Combinations   : {0, 1}