GetCultureInfo with unknown key no longer fails on Windows 10

Description

On Windows 10, CultureInfo.GetCultureInfo will no longer throw an exception for valid BCP-47 culture names, instead an Unknown Culture is returned. Invalid strings, i.e. non BCP-47 format, will still result in a CultureNotFoundException. We should review the code we have code that relies on the throwing behavior and see if we need to also check for any Unknown Cultures returned.

For details, see:

• https://social.msdn.microsoft.com/Forums/vstudio/en-US/70f01bf8-290b-43e3-a2ae-08870220c3c8/cultureinfogetcultureinfo-behavior-change-on-windows-10?forum=netfxbcl
• https://github.com/dotnet/corefx/issues/1669

Identified methods:

• EPiServer.Globalization.LanguageSelection.TryGetCulture()
• EPiServer.Framework.Localization.CultureInfoExtensions.TranslateCultureName()
• EPiServer.DataAbstraction.ILanguageBranchRepositoryExtensions.Load()
• EPiServer.Web.Routing.ContentRoute.TryGetCultureInfo()