Updated caliburn.micro

* Upgraded solution / project files to Visual Studio 2013
* Upgraded Caliburn.Micro 1.4 to Caliburn.Micro.Core 2.0.0-beta2
* Converted Caliburn.Micro.Logging to a portable class library
* Dropped support for TraceLogger since it is not support in a PCL
* Dropped SilverLight 4/5 and Windows Phone 7.1 support
* Added a key for strong name support for all assemblies