Make default logging threshold for Release be debug.

As discussed in issue freeorion#1575, there are currently not enough logs at the
info, warning and error level for the log files to be useful to testers.
Since we do not have separate targets for players, testers and devs,
this commit is setting all build types default logger thresholds to
debug.

util/Logger.h

@@ -146,11 +146,7 @@
 // The logging levels.
 enum class LogLevel {trace, debug, info, warn, error, min = trace, max = error};
 
-#ifdef NDEBUG
-constexpr LogLevel default_log_level_threshold = LogLevel::info;
-#else
 constexpr LogLevel default_log_level_threshold = LogLevel::debug;
-#endif
 
 FO_COMMON_API std::string to_string(const LogLevel level);
 FO_COMMON_API LogLevel to_LogLevel(const std::string& name);