* Includes updating the manifest to format 4. It turns out the manifest and .info files were not very good for providing information. A format update was required anyway so worked through the backlog of changes that would require a format change.
* Multiple database versions are now supported in the archive. Does't actually work yet but the structure should be good.
* Tests use more constants now that test logs can catch name regressions.
All tests local over SSH with rsync default compression, 4 threads and default compression on backrest. Backrest default is gzip = 6, assuming rsync is the same.
On a 1GB DB:
rsync time = 32.82
backrest time = 19.48
backrest is 171% faster.
On a 5GB DB:
rsync time = 171.16
backrest time = 86.97
backrest is 196% faster.
