Add an option to automatically add user-specified announce url to all torrents

[Unxed]

Imagine you have two peers in local subnet, 192.168.1.12 and 192.168.1.13. They both access the internet via NAT, so tracker sees them as NAT server ip. So they could not connect each other directly. Imagine that multicast is blocked so Local Peer Discovery won't solve the issue.

If qBittorrent could add announce url of local tracker, located in the same network (for example, http://192.168.1.14/announce), to all torrents, peer should see each other by their local addresses. Such local announce url can be specified in the advanced setting dialog for example.

[Ternia (twilite)]

Pretty useful feature, want it too.