nUpdate v4.0

• Removed nUpdate.ProvideTAP and nUpdate.WithoutTAP packages and replaced them with one nUpdate package
• Upgraded nUpdate package to .NET standard 2.0
• Upgraded all other packages and applications to .NET Framework 4.6.1 and applied the SDK project styles
• Fixed problems with TLS 1.2 and FTPS certificates in the administration
• Simplified the project structures
• Removed redundant dependencies to System.Windows.Forms and others