Normalize extension namespaces

The namespace of the following classes need to be SenseNet.Extensions.DependencyInjection:

[ ] SenseNet.Configuration.ConnectionOptionExtensions (repo: sensenet, project: SenseNet.Common)
[ ] SenseNet.ContentRepository.ContentNamingProviderExtensions (repo: sensenet, project: SenseNet.ContentRepository)
[ ] SenseNet.Security.Messaging.MessagingExtensions (repo: sn-security, project: SenseNet.Security)

SenseNet / sensenet