Preparation work for corruption/recovery testing

[LorenzoBoccaccia]

• changed upload/download format for saving one server round trip
• added sector/device characteristics to prepare for recovery testing
• added md5 page centric dump to make corruption visible in debug

first step if we want to test lock corruption would be to declare to sqlite the actual vfs invariants the changes follow what I understand of the specs here https://www.sqlite.org/draft/fileio.html#tocentry_50

[michalc]

The diff looks very odd for some reason - like every single line has been changed, even thought that also clearly not the case. Do you know what's happened / if anything can be done to tidy it?

[LorenzoBoccaccia]

a few hiccups with white spaces