Catfood Shapefile 2.00

Migrated to .NET Standard 2.0. Catfood Shapefile is now also released on NuGet at https://www.nuget.org/packages/Catfood.Shapefile/2.0.0. If you use an older version of .NET that does not support .NET Standard 2.00 please use the 1.60 release from GitHub.

Catfood.Shapefile 1.60

Fix from liborweigl to allow shapefile use after enumeration: #1