[csharp][aspnet5] AbstractCSharpCodegen base

This moves a bit of logic into a base type to prevent lots of
duplicates.

I've only converted csharp and aspnet5 generators, not csharp 2.0.

This base class should provide enough flexibility to support other C#
based client and server generators.

samples/client/petstore/csharp/SwaggerClientTest/Lib/SwaggerClient/src/main/csharp/IO/Swagger/Properties/AssemblyInfo.cs

@@ -0,0 +1,33 @@
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Windows;
+
+// General Information about an assembly is controlled through the following
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyTitle("Swagger Library")]
+[assembly: AssemblyDescription("A library generated from a Swagger doc")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("Swagger")]
+[assembly: AssemblyProduct("SwaggerLibrary")]
+[assembly: AssemblyCopyright("No Copyright")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible
+// to COM components.  If you need to access a type in this assembly from
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// Version information for an assembly consists of the following four values:
+//
+//      Major Version
+//      Minor Version
+//      Build Number
+//      Revision
+//
+// You can specify all the values or you can default the Build and Revision Numbers
+// by using the '*' as shown below:
+// [assembly: AssemblyVersion("1.0.*")]
+[assembly: AssemblyVersion("1.0.0")]
+[assembly: AssemblyFileVersion("1.0.0")]