via the new PackageReference nodes.
The upsides here are
1) the MS package downloading and validation is much faster than the premake version
2) since the config is in the project file instead of packages.config which means
multiple nuget projects can sit in the same folder.
Fixed nuget code to only use PackageReference on .net projects,
and moved validation code into the module where it belongs.
vs2010 (and above) has an issue where if the vcxproj file
isn't modified but the.vcxproj.filters is modified during
premake, then VS doesn't notify the user that the project has
changed. This can occur if the only change to a project is
with the vpaths. Before this fix, the user would be need to
manually unload and reload the project to pick up the change.
This VS workaround checks for the case where the vcxproj.filters
file is modified but the .vcxproj file is not. At which point
premake preforms a touch on the .vcxproj file to trigger the IDE.
