Add Xamarin and WinStore/Phone support with PCL Profile 259 (.NET 4.5)

Adds .NET 4.5 portable profile 259.
This profile is widely used and well supported by Xamarin for iOS and Android, as well as all the Windows targets for PC and mobile.

Target: portable-net45+netcore45+wpa81+wp8+MonoAndroid1+MonoTouch1

The biggest challenge was fixing all the reflection code to support the new reflection API around [TypeInfo](http://blogs.msdn.com/b/dotnet/archive/2012/08/28/evolving-the-reflection-api.aspx). This API is not supported in the current portable profile 136 for .NET 4.0, since it is only available in .NET 4.5 and later.

Portable nuget now has the following targets: .NET 3.5, .NET 4.0 (pcl) and .NET 4.5 (pcl)

Some cleanup:
* Rename PORTABLE compile condition to PORTABLE40, and add PORTABLE45
* Rename portable projects to Common.Logging.Portable.2010-netxx for consistency
* Change output paths to /build/portable/
* Use separate intermediate output paths for portable projects to avoid "already in use" build errors in Visual Studio

I particularly want review on the following changes:
* [Remove net40 target in nuget](https://github.com/anjdreas/common-logging/commit/a15d76afcbff8b724682536befd8682fb3046241)
* [Updating CommonAssemblyInfo](https://github.com/anjdreas/common-logging/commit/fc137a57e4fb80c851b70e53b18679f98e702855)
* [Returning "N/A" for thread ID in ExceptionFormatter.cs](https://github.com/anjdreas/common-logging/commit/31247394b81969d47b96cd0f2e31820378585670)
* [Translations of reflection code to new reflection API](https://github.com/anjdreas/common-logging/commit/31247394b81969d47b96cd0f2e31820378585670)
* [Delete seemingly unused portable project](https://github.com/anjdreas/common-logging/commit/6adda64a0f45fef73dbf130c3ad4d8ed220c2559)