Microsoft/Xamarin.Dropbox.Apiv4.5.3.1

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✓ Verified.NETPortable0.0-net40+sl50+wp80+win80+wpa81.NET Std2.0Xamarin.iOS1.0Xamarin.Mac3.8

Portable class library for accessing the Dropbox v2 API specifically for Xamarin.Android and Xamarin.iOS to fix a depedency issue with the standard package. Bumps the minimum version of Microsoft.Bcl.Build to v1.0.21 and adds .Net standard 2.0 version of the library