Require tags for NuGet package definitions

[TimHess]

One of the features of #1012 is validation that all NuGet packages produced in Steeltoe have a description filled in. This can also be applied for Tags, but first we will need to add tags to all projects. The line below (which may or may not be merged with the PR) will need to be active in this section

<Error Text="The 'PackageTags' property must be set for packable project '$(MSBuildProjectName)'." Condition="'$(PackageTags)' == ''" />