Add .NET Core 2.0 and .NET Standard 2.0 builds

Author: hazzik

Tools/packages.config

@@ -7,6 +7,6 @@
   <package id="NUnit.Extension.NUnitV2ResultWriter" version="3.6.0" targetFramework="net461" />
   <package id="NUnit.Extension.TeamCityEventListener" version="1.0.2" targetFramework="net461" />
   <package id="NUnit.Extension.VSProjectLoader" version="3.6.0" targetFramework="net461" />
-  <package id="CSharpAsyncGenerator.CommandLine" version="0.8.1" targetFramework="net461" />
+  <package id="CSharpAsyncGenerator.CommandLine" version="0.8.2" targetFramework="net461" />
   <package id="vswhere" version="2.1.4" targetFramework="net461" />
 </packages>

build-common/NHibernate.props

@@ -24,5 +24,7 @@
 
     <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
     <TreatSpecificWarningsAsErrors />
+    
+    <DisableImplicitPackageTargetFallback>True</DisableImplicitPackageTargetFallback>
   </PropertyGroup>
 </Project>