Support .NET 4.6.1 as well as NetStandard 2.0

Author: Tomas Lycken

src/RdbmsEventStore.EFCore/RdbmsEventStore.EFCore.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFrameworks>net461;netstandard2.0</TargetFrameworks>
     <Version>0.0.0</Version>
     <PackageVersion>0.0.0</PackageVersion>