Chore: update man pages and docs

[FranciscoPombal]

Related comment: https://github.com/qbittorrent/qBittorrent/pull/12083#issuecomment-592010800

Man pages and general documentation about qBittorrent's flags is severely out of date. It would be helpful to document all the new flags that qBittorrent now supports. The description should be clear and concise, but not miss out on any important detail of how exactly they change qBittorrent's behaviour.

It is not very nice to ship bundled man pages with very incomplete information (and some of it could now be inaccurate even).

@Chocobo1 @glassez I assigned you because you have a lot of understanding of qBittorrent's internals and recently participated in a related PR. Feel free to un-assign though.