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
Removed the ``__func__`` changes, so this is the only empty new-line and I remove no emtpy new-line. Sorry I'm a tad frustrated that testing of the larger pulls is a little slow and that coding-style stuff is just low-/no-priority.