NuGet: <licenseUrl> element will be deprecated

[jonorossi]

NuGet outputs the following warning during packaging. We should change to specify the license.

WARNING: <licenseUrl> element will be deprecated,please consider switching to specifying the license in the package. Learn more: https://aka.ms/deprecateLicenseUrl.

While here it would be good to reinstate the Castle logo on the package, I know the icon can now be embedded into the package which is definitely much better than pointing to the web site.

[stakx]

According to NuGet/Home#7509 (comment) and NuGet/Home#7547 tools aren't actually ready for <license> yet, and switching now could result in a corrupted NuGet package. We should perhaps track those issues and wait a little longer.

[jonorossi]

@stakx the warning has been there for quite a while and the registry doesn't support it yet, wow.

We should probably just suppress NU5125 like everyone else (including the ASP.NET team) is doing and move on for now, sounds like it'll be a year or two before we can do much while the new tools get out there when it happens.