v4.2.0

1. Enhancement: Changed logic of SiteMapLoader so passing null or empty string causes it to lookup the SiteMapCacheKey from ISiteMapCacheKeyGenerator rather than throw an ArgumentNullException. This makes it easier to implement features with an optional SiteMapCacheKey value.
2. Feature: Added SiteMapCacheReleaseAttribute action filter attribute that can be used on controller actions to clear the cache after executing the controller action and before the view is processed.
3. Bug: Fixed SiteMapCacheKey property on SiteMapTitleAttribute because it was not available publicly.
4. Documentation: Added readme file to obsolete MvcSiteMapProvider package with instructions on how to remove it and/or replace it with the MvcSiteMapProvider.MVCx packages.
5. Feature: Added a web.config setting named "MvcSiteMapProvider_EnableResolvedUrlCaching" for use with the internal DI container that can be used to globally disable URL resolution caching.
6. Bug: AttributeDictionary was throwing exceptions when trying to add values from the presentation level. This was unintended, as it was supposed to allow changes that are valid only for the current request.
7. Bug: Fixed visibility for /sitemap.xml endpoint so each URL will function individually rather than being blocked if the parent node doesn't have visibility. The ACL modules still block access to their child nodes as expected.
8. Enhancement: In the /sitemap.xml endpoint, duplicate URLs are no longer sent to the output, as there would be no value in listing the same URL twice.
9. Bug: In the /sitemap.xml endpoint, fixed the default baseUrl setting so it will take into consideration when an application is being hosted as a sub application.
10. Enhancement: Removed unnecessary caching from SiteMapNodeUrlResolver.
11. Bug: Fixed thread safety of the cache of ControllerTypeResolver.
12. Bug: Fixed cache key names for RouteValueDictionary and AttributeDictionary.