* Improves code readability.
* Improve documentation.
* Fix "docker stop" doesn't terminate qbt gracefully which could lead to
data corruption.
* Provide correct/working bittorrent listening port by default.
* Make use of qbt profile option instead of hacking environment
variables.
* Simplify build steps.
PR #16976.
It uses the latest available version for libtorrent and builds both libtorrent and qBittorrent with Cmake + ninja
The legal notice must be accepted trought an environment variable called LEGAL and passed to docker when the container is run, to set it true one must set "LEGAL=accept"
PR #16828.
