Cleanup code, get rid of antipatterns

[garretraziel]

While we are using async, there is still a lot of antipatterns - callback hell (everywhere), not-error-first callbacks (mainly memdb) etc.

Quite often, there is unnecessary anonymous function - when function a could take function b as a callback, but instead there is an anonymous function that only calls b in its body. Promises could be also used.

Another thing is that there is often not clear where logging should take place. I think that the best way is to propagate all err objects to topmost function and log them using winston only after they aren't passed further.