Cherry-pick Nuget Net47 changes

[QilongTang]

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Purpose

This fix is needed so devs can continue to build R2019 branch with latest DynamoCore references.

FYI: @mjkkirschner @Dewb @ZiyunShang @AndyDu1985 I think the nuget folder change in DynamoDS/Dynamo#9250 impact is larger than I thought since DynamoRevit legacy branches other than master are setup in a way that always consumes latest-beta of DynamoCore nugets, so the folder change is automatically consumed downstream by all of these repos. Although I think only R2019 branch should be cherry-picked because R2019 branch is supposed to have moved to .Net 47.

However, I am not sure what we should do to R2018, R2017 etc because it is broken there as well unless we provide nugets containing dlls built both with Net45 and Net47.

Declarations

Check these if you believe they are true

• The code base is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• Snapshot of UI changes, if any.

Reviewers

FYIs