Fixed CodeAnalysis errors by making CodeAnalysis run only in .NET 4.5 build

* Fixed CodeAnalysis errors by making CodeAnalysis run only in .NET 4.5
* StyleCop related cleanups<p><a href="https://github.com/WindowsAzure/azure-sdk-for-net/pull/360">https://github.com/WindowsAzure/azure-sdk-for-net/pull/360</a></p>
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