Small fixes for dialogs. Small fixes for log appending (GUI). Using steady_clock instead std hiresclock.

Proper escaping for filename at displaying error during saving logs.
Added ask dialog when file exists during saving log.
Use std::chrono::steady_clock instead std::high_resolution_clock because
many systems uses non-monotoning clock as hires clock.
Added workaround for Windows and MSVC 2012 for steadyclock.