Fix packing readme and analysis recommendations

[Shane32]

On NuGet.org, the readme file is not appearing. This is because the PackageReadmeFile did not get set while building. This is because the condition IsPackable == true does not work if IsPackable is not explicitly set, even though when it is not set, it is implied to be true for the purposes of packing and within ItemGroups. This also caused the analysis to be disabled.

The analysis mode revealed that some xml comments on some old code was missing.

I ran the pack locally and examined the output to be sure it built correctly this time.

It is not critical to release 7.0.1, as there are no breaking changes and the 7.0.0 code should work just fine. Nevertheless, we can release 7.0.1 if you think we should @sungam3r , before everyone downloads it. Or, we could wait a week or two to see if there are any other issues that need to be addressed.