Need new backup format for XA 1.1 data pool
The current backup/restore is designed for XA 1. This has issues for XA 1.1.
The fix described in #140 will make the XA 1.1 backup/restore work on V6 backups files (compatible with the latest XA 1 backup). However, it will be inefficient. A new backup format is needed for efficient backup/restore of XA 1.1.
The new format is not going to supplant XA 1, so it should not be labeled V7. It may be possible to call it "V6.1" though a disconnected numbering scheme would be preferable.
It should not be necessary to make the new format readable by XA 1, but this should be relatively easy, either using the IntFile mapping suggested in #140, or just by specifying gNodes, since this format allows gNodes to be specified. The latter is less desirable, as it can lead to files growing larger than they should in the XA 1 format.