Sample archive extraction total progress fix

[David Healey]

I noticed in the expansion handler's install callback that the (undocumented) TotalProgress value is wrong, it caps out at about 0.4.

Poking around in the code I spotted that it seems to just be tracking the reading of the first bit of the file. The actual decompressing/writing progress wasn't contributing to the total progress value at all.

I've made a PR that has TotalProgress tracking the decompressed bytes instead. This gives much more pleasing results. I've tested it with single and multi-part hr archives.

[dannytaurus]

@David-Healey Looking forward to getting into expansions. Glad you're around for questions!