Finish conversion to NX.I18n string

A few places still not using NX.I18n.

• Review all usage of NX.Messages API
• Review all usage of NX.Dialogs API
• Review all usage of NX.Security API
• -Review all usage of 'waitMsg:' specifications

Classes in nexus-rapture-plugin:

• NX.view.AboutWindow
• NX.view.Authenticate
• NX.view.ExpireSession
• NX.view.UnsupportedBrowser
• NX.view.header.AdminMode
• NX.view.header.BrowseMode
• NX.view.header.UserMode
• NX.view.header.Help
• NX.view.header.Messages
• NX.view.feature.NotFound

Classes in nexus-coreui-plugin:

• NX.coreui.controller.Metrics
• NX.coreui.controller.NuGetRepositorySettings

Pending further investigation fore coreui and proui modules.