Fixes #130, respect AllowAnonymous attribute when it is used. Also added AllowAnonymous attribute to XmlSiteMapController so it will allow search engines if a global AuthorizeAttribute is used.
Fix #141 (if Url contains 'http' not only in schema part, but also in path, then <loc> value generated as relative path, instead of absolute in sitemap.xml)
Changed compilation constant logic in MvcSiteMapProvider.csproj to match that in v4.