Move streamwrappers to seperate files and put them in a namespace

apps/files_external/lib/amazons3.php

apps/files_external/lib/dropbox.php

apps/files_external/lib/ftp.php

apps/files_external/lib/google.php

apps/files_external/lib/swift.php

apps/files_external/lib/webdav.php

apps/files_sharing/lib/sharedstorage.php

lib/archive/tar.php

lib/archive/zip.php

lib/base.php

lib/files/stream/close.php

lib/files/stream/dir.php

lib/files/stream/staticstream.php

tests/lib/streamwrappers.php