Nice page names and titles for pages outside spaces

Displaying XWiki pages space name and document name is not very meaningful in Workspaces for pages outside a workspace. Instead we should have a list of nice names adapted to the application. It concern :

• Main.WebHome (authenticated/unauthenticated ?)
• XWS.MySpaces
• XWS.Directory
• XWiki.${Username}
• XWiki.XWikiPreferences (all sections)
• XWiki.Registration

Possible implementation could be to rely on internationalization message keys