Use NuGet 2.7 automatic package restore. Get latest NuGet.exe when missing.
Use NuGet package for nunit-console.exe instead of relying on one being installed on system.
Add NuGet.Lucene-net40.csproj to target .NET 4.0 with Bcl/Async.
Add dependencies to nuspec.
Side-step NuGet $version$ property which uses 4 version numbers to use correct semver version.
Turn off warnings about missing documentation.
Fix xml comments.
Use real path, not computed path, when loading package and metadata from filesystem.
Explicitly delete package being replaced when re-indexing a modified package.

Works around bug in Lucene.Net.Linq where a modified entity wins
over explicitly added entity within session.
Change the LastUpdated/Published date to derive from the Created date

In most cases, I'm fairly certain the package will never be modified, only ever created.
It's possible that the Nuget PhysicalFileSystem lib should be changed to fix this and return the
created date if the file has never been modified. Not sure how it would detect this, but we can pass
it up the chain if that makes more sense.