FeedService service caches aggressively all public methods of IFeedService
 Nuget feeds now cache their Find FindLatests methods results with a NugetFeedBase.
Fixed FileSystemFeedTester test by adding distinguisher for a nuget stability in the provided caches. Caching moved from Dict to Fubu Cache
Merged in #76 and rebased the connectivity cleanup on top.
Solution now allows override the default NugetFolderCache