Allow some way to specify instance name

[jagannatharjun]

While fooling around with qbittorrent sources, I always have my main instance of an official qbittorrent downloading something but since qbit don't support multiple instance I always have to manually change the instance name of my dev qbittorrent to allow multiple qbit instance.
Can't we do something to specify instance name to allow multiple instances without touching qbit sources?
f.e when developing I always start qbittorrent with a custom profile folder, so maybe an Environment variable from where qbittorrent can read the instance name or command line arg (adding cmdline option can be little tedious but I didn't fully think that through).