json: Use project references instead of nuget references

In order to catch problems due to breaking changes in UnitsNet that was not observed
due having a nuget dependency pointing to an older version of UnitsNet.
This way we always build against the latets (local checked out) UnitsNet code.

Caveat: The nuget dependency version can no longer be controlled and will always
point to the latest version (the one in the checked out code). This means pushing a new
Json nuget will also increase its dependency version if a newer one is available.
I don't currently know of a way to both get project reference AND control the nuget dependency
version, but I consider this a fair tradeoff as it is fair that taking on a newer version of Json lib will
require a newer version of UnitsNet too.

Author: angularsen

UnitsNet.Serialization.JsonNet/UnitsNet.Serialization.JsonNet.Signed.csproj

@@ -13,7 +13,8 @@
     <AssemblyOriginatorKeyFile>$(MSBuildProjectDirectory)\..\UnitsNet.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
 
+  <!-- Signed project references, will also generate the corresponding nuget dependencies -->
   <ItemGroup>
-    <PackageReference Include="UnitsNet.Signed" Version="3.65.0-alpha3" />
+    <ProjectReference Include="..\UnitsNet\UnitsNet.NetStandard10.Signed.csproj" />
   </ItemGroup>
 </Project>

UnitsNet.Serialization.JsonNet/UnitsNet.Serialization.JsonNet.csproj

@@ -1,7 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <Import Project="UnitsNet.Serialization.JsonNet.Common.props" />
 
+  <!-- Unsigned project references, will also generate the corresponding nuget dependencies -->
   <ItemGroup>
-    <PackageReference Include="UnitsNet" Version="3.65.0-alpha3" />
+    <ProjectReference Include="..\UnitsNet\UnitsNet.NetStandard10.csproj" />
   </ItemGroup>
 </Project>