Update csproj a bit

Author: joemphilips

NBitcoin/NBitcoin.csproj

@@ -20,7 +20,7 @@
 		<EmbedUntrackedSources>true</EmbedUntrackedSources>
 	</PropertyGroup>
 	<PropertyGroup>
-		<TargetFrameworks>netcoreapp2.1;netstandard2.0</TargetFrameworks>
+		<TargetFrameworks>net461;net452;netstandard1.3;netstandard1.1;netcoreapp2.1;netstandard2.0</TargetFrameworks>
 		<TargetFrameworks Condition="'$(BuildingInsideVisualStudio)' == 'true'">netstandard2.0</TargetFrameworks>
     <TargetFrameworks Condition="'$(TargetFrameworkOverride)' != ''">$(TargetFrameworkOverride)</TargetFrameworks>
 		<NoWarn>1591;1573;1572;1584;1570;3021</NoWarn>