Revert namespace change

Microsoft guidelines indicate that third party developers should never use the System.* namespace as this is reserved for .NET Framework code, the .NET Team would not be aware of any third party libraries using this and if they implemented a class with the same name then this would cause naming conflicts.
That given, this also means that v3 is backward compatible with v1 of Range

Linear and DiscreteLinear Range Implementations

Namespace has changed so the major version has been incremented to v2.0.0
Includes Linear and DiscreteLinear Range with FindClosestValue methods