title: Unity - NuGet package gets auto-removed
body: <p>I've created an Unity project, and want to use the OpenNI wrapper from here <a href="https://github.com/falahati/NiWrapper.Net" rel="nofollow noreferrer">https://github.com/falahati/NiWrapper.Net</a>.
  After adding the NuGet package in JetBrains Rider it appears and is installed correctly (is usable) but after a minute or two -the package disappears and Rider warns me that it can't resolve symbols from the wrapper and the namespace OpenNIWrapper could not be found... But what's strange it still appears in "Packages" of the project.</p>
  
  <p>I'm using the newest MacOS Mojave, already tried on VS for Mac, MonoDevelop and in Rider... I've tried removing the project and creating it from scratch, tried to change API Compatibility Level in Unity - both 4.0 and 2.0 don't work.</p>
  
  <p>I noticed that it does some kind of auto-synchronization or build and deletes the package from .csproj file.</p>
  
  <p>Basically I've run out of ideas and couldn't find any solutions anywhere... I'll appreciate any help, thanks :)</p>