Support for analyzer nuget

[sailro]

See the following nuget: https://www.fuget.org/packages/Microsoft.Unity.Analyzers

This is a special nuget for a Roslyn Analyzer (so the interesting part is that an analyzers folder is used instead of the expected lib one)

So fuget is currently confused to display/diff any assembly/type info.

File hierarchy for this nuget:

.signature.p7s
Microsoft.Unity.Analyzers.nuspec
[Content_Types].xml
analyzers\dotnet\cs\Microsoft.Unity.Analyzers.dll
package\services\metadata\core-properties\f9366dce472b4a0fb34e4ed667c83570.psmdcp
tools\install.ps1
tools\uninstall.ps1
_rels\.rels

So it's probably necessary to review those code parts: https://github.com/praeclarum/FuGetGallery/search?q=%22lib%22

Documentation: https://docs.microsoft.com/en-us/nuget/guides/analyzers-conventions#analyzers-path-format