Upgrade to target .NET Standard#305

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mgurlitz wants to merge 3 commits intomicrosoft:mainfrom

mgurlitz:feat-standard

Commits on Dec 19, 2019

Upgrade projects to .NET Standard
mgurlitz
committed

Commits on Jan 8, 2020

Remove unused class and rename internal
mgurlitz
committed

Commits on Jan 10, 2020

Remove protected internal keyword
mgurlitz
committed