Adds request timing to response wrapper

Adds the ability to show request timings in the response wrapper.
This includes the request start, end, and duration.
Exposes `RequestStart`, `RequestEnd` and `RequestDuration` on the `Response` class.

Author: surgicalcoder

GoLive.Generator.ApiClientGenerator.Tests.WebApi/ApiClientGenerator.json

@@ -24,6 +24,7 @@
   "RouteTemplate":"/api/{area:exists}/{controller=Home}/{action=Index}/{id?}",
   "ResponseWrapper" :{
     "Enabled": true,
+    "ShowTimings": true,
     "ExtractHeaders":{
       "CorrelationId": "X-Correlation-Id"
     }