Swift/Echoes doesn't actually need Echoes.dll; allows us to keep supporting .NET Standard 1.3

Author: dwarfland

Source/Swift.Echoes.Standard.elements

@@ -51,11 +51,7 @@
     <WarnOnCaseMismatch>True</WarnOnCaseMismatch>
     <DefineConstants>SIGN</DefineConstants>
   </PropertyGroup>
-  <ItemGroup>
-    <Reference Include="Echoes">
-      <Private>True</Private>
-    </Reference>
-  </ItemGroup>
+  <ItemGroup></ItemGroup>
   <ItemGroup>
     <Compile Include="__AssemblyInfo.swift" />
   </ItemGroup>

Source/Swift.Echoes.elements

@@ -57,9 +57,6 @@
     <Reference Include="System.Core" />
     <Reference Include="System.Data" />
     <Reference Include="System.Xml" />
-    <Reference Include="Echoes">
-      <Private>True</Private>
-    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="__AssemblyInfo.swift" />