Listen on https://localhost:5001 by default when a default HTTPS certificate is available

[danroth27]

Absent any configuration, by default Kestrel listens on http://localhost:5000. Kestrel by default should also listen on https://localhost:5001 if a default HTTPS certificate is available (i.e. on a dev machine with the .NET Core SDK and the ASP.NET Core HTTPS development certificate installed).

[Tratcher]

IDefaultHttpsProvider will need an IsAvailable property or TryConfigure method. Today's ConfigureHttps throws if the cert is missing.