added redirect for legacy download URL
added redirect for legacy download URL

mtian/SiteExtensionGallery,kudustress/NuGetGalleryOptmized,ScottShingler/NuGetGallery,kudustress/NuGetGallery2,skbkontur/NuGetGallery,JetBrains/ReSharperGallery,KuduApps/NugetGallery21Fx45-DeleteMe,JetBrains/ReSharperGallery,mtian/SiteExtensionGallery,KuduApps/NugetGallery16Fx45-DeleteMe,grenade/NuGetGallery_download-count-patch,grenade/NuGetGallery_download-count-patch,projectkudu/SiteExtensionGallery,kudustress/NuGetGallery,KuduApps/NuGetGallery,ScottShingler/NuGetGallery,kudustress/NuGetGallery2,ScottShingler/NuGetGallery,projectkudu/SiteExtensionGallery,KuduApps/NugetGallery21Fx45-DeleteMe,mtian/SiteExtensionGallery,JetBrains/ReSharperGallery,grenade/NuGetGallery_download-count-patch,KuduApps/NugetGallery16Fx45-DeleteMe,kudustress/NuGetGalleryOptmized,skbkontur/NuGetGallery,KuduApps/NuGetGallery,kudustress/NuGetGallery,projectkudu/SiteExtensionGallery,KuduApps/NuGetGallery,KuduApps/NuGetGallery,skbkontur/NuGetGallery,KuduApps/NuGetGallery