Design Patterns in C# - update to VS 2019

Updated solution to VS 2019. Spot-checked examples.

Design Patterns in C# - Support VS 2017 solution

Upgraded the solution file to VS 2017, spot-checked examples.

Design Patterns in C# - updated solution to VS 2015

Updated solution file and spot-checked running examples.

Design Patterns in C# - works with Visual Studio 2012

Confirm that things work in Visual Studio 2012 (still). May be setup issues with database and web service.