add-credentials for a domain

[kostrse]

AFAIK, currently Paket support settings credentials only to exact NuGet URLs.

It could be useful to define credentials for a whole domain (or possibly URL wildcard).

Use case:
Private NuGet server with multiple feeds, each feed requires the same credentials.
VSTS works this way for example. One VSTS account (domain name) may have several NuGet feeds.

[jbaehr]

We have the same use case. I would also very much appreciate this improvement!