Add arguments to the upload data & logs commands to only upload a chunk of the data & log files

The nodes are struggling to upload the entire log & data files, plus this is a big data soak.

Change these commands to allow a chunk of `offset/length`, or `-length` to be specified.

All arguments are in bytes.

`offset/length` allows an arbitrary chunk of _length_ bytes starting at _offset_ of the file to be uploaded.

`-length` means the last _length_ bytes of the applicable file.