Nuget CefSharp.Common.targets error message to clarity that you must set the solution and platform target

Resolves #2287

Author: amaitland

NuGet/CefSharp.Common.targets

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Target Name="PlatformCheck" BeforeTargets="ResolveAssemblyReferences" Condition="(('$(Platform)' != 'x86') AND ('$(Platform)' != 'x64') AND ('$(Platform)' != 'Win32') AND '$(CefSharpAnyCpuSupport)' != 'true')">
-    <Error Text="$(MSBuildThisFileName) will work out of the box if you specify platform (x86 / x64). For AnyCPU Support see https://github.com/cefsharp/CefSharp/issues/1714" />
+    <Error Text="$(MSBuildThisFileName) contains unmanaged resoures, set your project and solution platform to x86 or x64. Alternatively for AnyCPU Support see https://github.com/cefsharp/CefSharp/issues/1714" />
   </Target>
 
   <Target Name="FrameworkVersionCheck" BeforeTargets="ResolveAssemblyReferences" Condition="(('$(TargetFrameworkVersion)' == 'v4.5.1') OR ('$(TargetFrameworkVersion)' == 'v4.5') OR ('$(TargetFrameworkVersion)' == 'v4.0'))">