Increase transfer status to see the status of all the files

If we use transfer dataset with multiple files (or a directory) the transfer id will show information about the last not completed transfer.

However, on the HSM use case it makes sense to have a complete list of statuses for each file. This way we can notify that a file can be already be used on the target backend.

We plan to have transfer_statuses (tid), returning a vector of status (filename, status, last bw, total bw):

1. A vector with file name and status, actually the file name is not stored so it should be made available.
2. The BW obtained on the transfer of the file. This is also not stored, as we only store the last block BW. But it could be interesting to have it.

The BW can be calculated from the initial submit of the operation, and the complete status. So it will include time waiting in the queue. The are pro's and con's about that.