SoulseekQt seems unable to use more than one CPU core

I wouldn't say that this is critical, but I've noticed that even when slsk is "working hard" (ie, starting up and scanning shares, queueing a large directory, etc.), it will only occupy one core of my two-core system (and quite fully at that).

I think that moving forward in the future, with multi-core systems really becoming dominant, this should be addressed. On systems with even more cores than my measly two, which are increasingly common, this is really a big detriment to the performance of the client.

I'm hardly up in arms about this, but I figure it's worth bringing up.

Much love to nir and all the devs, and thanks a ton!