Merge pull request #315 from markcowl/bug311

Bug 311
Added Common.Tracing.Etw and Common.Tracing.Etw.Test projects
Patchable
Implemented EtwTracingInterceptor class logic and added appropriate integration tests.
Added NuSpec and NuSpec.Proj files for Microsoft.WindowsAzure.Common.Tracing.Etw
Added readme.txt file
Imported general library targets and cleaned up project file
Changed SendRequest and ReceiveResponse to be virtual to allow for further configuration by end users
Changed ETW NuGet package name to match other Windows Azure packages
Fixed misc. issues raised by FxCop
Merge branch 'dev' of https://github.com/WindowsAzure/azure-sdk-for-net into etw
Cleanup
XSCL 2.1.0.4 - Hotfix
Fix for Issue WindowsAzure/azure-sdk-tools#2150
Merge pull request #318 from kenegozi/patch

Patchable
Moved common tracing functionality into CloudTracingExtensions and added tests
Updated changelog
Merge pull request #323 from markcowl/bug2150

Fix for Issue WindowsAzure/azure-sdk-tools#2150
Unit test fixes due to server changes
Updates based on code review.