init.cpp: log fee estimates filename on error

- small changes to Shutdown(), buffer ``__func__``, which is now used in
  all LogPrintf() calls and format for better readability
- order using namespace alpabetically
I understand that, but I hope you also understand that pulls that fix issues or add important functionality rank a lot higher. We don't want to break those unnecessarily, it's hard enough as it is.

Anyhow: if you want your commits to be merged quickly try to fix bugs!