Make +canHandleURL: private for now

Note sure it's actually of use to clients
Tweak URL-handling to be a category on CK2FileManager
Make +ck2_isFTPURL private to FTP code
Remove CK2RemoteURL in favour of +[CK2FileManager setTemporaryResourceValue:forKey:inURL:]
Merge branch 'curlhandle-4' of github.com:karelia/ConnectionKit into curlhandle-4