Using packages.config for our PCL project template

Fixes bug#52085 - Getting popup error message while creating multi-platform 'Single for all platform'

This avoids to get the "nvalid framework version '.0'" error from the NuGet.Client tools
And also making sure the version targets are correctly defined still when the NuGet.Build.Packages.targets
are imported after

Author: adalon

src/VisualStudio/NuGet.Packaging.VisualStudio.15/Templates/Projects/PortableClassLibrary/PortableClassLibrary.csproj

@@ -13,7 +13,6 @@
     <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <TargetFrameworkProfile>Profile111</TargetFrameworkProfile>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
-    <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>

src/VisualStudio/NuGet.Packaging.VisualStudio.15/Templates/Projects/PortableClassLibrary/PortableClassLibrary.targets

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
-  <Target Name="GetPackageVersion" Returns="$(PackageVersion)">
+  <Target Name="SetPackageVersion" BeforeTargets="GetPackageVersion" Returns="$(PackageVersion)">
     <!-- NOTE: customize to determine your package version more dynamically -->
     <PropertyGroup>
       <PackageVersion>1.0.0</PackageVersion>