[Azoth Xoox] Prefer QByteArray::isEmpty().
[Azoth Xoox] Async threaded avatars saving.
[Azoth Xoox] Code style fixes.
[Azoth Xoox] Update incoming PEP avatar iff it's not null.
[Aggregator BF] Migrate to util/sys/paths.h.
[Util] Actually handle the UserDir::LC.