tests: added DNET_IO_FLAGS_COMMIT test
recovery: recover ts and user_flags
ext: optimized blob_read()

Previous implementaion had rather big overhead but had an advantage of
being simple - it has single code path for compressed and non-compressed
data.
Now it's time to split this single codepath for more efficient
implementaion of common case - read of non-compressed data.
ext: lookup now supports extended format
recovery: unify file naming
recovery: do not show zero counters
recovery: do not use removed ctx.node
dnet: simplify dnet_send_file_info_without_fd()

Also by providing '\0' as filename this fixes null pointer exception
that can be reproduced via ioclient -L.