Several improvement and fixes: image_tag check for linux- prefix, login procedure for custom registry, --docker-username normalization and --dns aks option documented at usage()
Several improvement and fixes: image_tag check for linux- prefix, login procedure for custom registry, --docker-username normalization and --dns aks option documented at usage()

dotnet-architecture/eShopOnContainers,albertodall/eShopOnContainers,albertodall/eShopOnContainers,dotnet-architecture/eShopOnContainers,dotnet-architecture/eShopOnContainers,skynode/eShopOnContainers,skynode/eShopOnContainers,skynode/eShopOnContainers,dotnet-architecture/eShopOnContainers,albertodall/eShopOnContainers,skynode/eShopOnContainers,albertodall/eShopOnContainers,skynode/eShopOnContainers,dotnet-architecture/eShopOnContainers,albertodall/eShopOnContainers