Allow to set min/max upload rate limits per torrent

[sefininio]

Currently, the user can only set min/max upload rate limits on a general level, that applies to the aggregate of all active torrents.
Would love to see a similar rate limit on a per-torrent level - sometimes you want to set a high limit for the aggregate, but set a lower limit for a specific one to avoid being banned.

[vilanele]

Hello, to add up on this, if I start 2 torrents and set a min = max = 1000 ko/s limit for example, most of the time one torrent get almost all brandwidth while the other only gets few ko. It would be nice to have a per-torrent min/max. Great work by the way enjoying your soft