Fix for GenericProcessor.GetPropertyValue to handle null values coming from the external data store

Added a lib folder at the root of the project with a readme to add a copy of Sitecore.Kernel and Sitecore.Logging. Updated references to pull from this location. Removed the sc.lib solution folder as there was nothing actually in use there. Updated ignore rules to ignore the TDS BuiltFiles artifacts. Fixed an issue in GenericProcessor.GetPropertyValue to handle null values coming from the external data store.