Fix#3124Fix#3004
Instead of loading a set 7 days of history. Better performance when there are lots of messages, and better context when friends haven't talked in over a week.
Removed historyBaselineDate, introduced in deb8440c6a to fix duplicate messages, but duplicate messages were very likely fixed by https://github.com/qTox/qTox/pull/4607.
Also refactored history loading.
Revert needed, since otherwise there is no way to do automatic sorting
of includes.
Also reverted change to the docs, as leaving it would make incorrect
docs.
In case of conflicts, includes were sorted according to the coding
standards from #3839.
This reverts commit b4a9f04f92.
This reverts commit 5921122960.
qTox will automatically import the old history on startup.
This new database code is much more robust.
It is very resilient and will not corrupt or disappear after a crash or
power failure, unlike the old code.
The on-disk database format is also much more compact now.
The database sync option in the advanced settings has been removed,
we know run many database operations asynchronously so performance
should not be a problem anymore, but we always ensure resiliency
in case of abrupt termination, so there is no tradeoff anymore.
