Fixes #289, bug in MvcSiteMapProvider.Web install.ps1 where missing appSettings, system.web, system.web.webPages.razor, and system.webServer elements were not being added to the configuration element in the XML. Also fixed logic in install.ps1 and uninstall.ps1 so it will install or uninstall the MVC >= 4 sections without having to update the code for future versions of MVC.