Replace logging backend to log4rs and add log rotation (#1789)

* Replace logging backend to flexi-logger and add log rotation
* Changed flexi_logger to log4rs
* Disable logging level filtering in Root logger
* Support different logging levels for file and stdout
* Don't log messages from modules other than Grin-related
* Fix formatting
* Place backed up compressed log copies into log file directory
* Increase default log file size to 16 MiB
* Add comment to config file on log_max_size option

config/src/comments.rs

@@ -367,7 +367,7 @@ fn comments() -> HashMap<String, String> {
 	retval.insert(
 		"stdout_log_level".to_string(),
 		"
-#log level for stdout: Critical, Error, Warning, Info, Debug, Trace
+#log level for stdout: Error, Warning, Info, Debug, Trace
 ".to_string(),
 	);
 
@@ -381,7 +381,7 @@ fn comments() -> HashMap<String, String> {
 	retval.insert(
 		"file_log_level".to_string(),
 		"
-#log level for file: Critical, Error, Warning, Info, Debug, Trace
+#log level for file: Error, Warning, Info, Debug, Trace
 ".to_string(),
 	);
 
@@ -399,6 +399,14 @@ fn comments() -> HashMap<String, String> {
 ".to_string(),
 	);
 
+	retval.insert(
+		"log_max_size".to_string(),
+		"
+#maximum log file size in bytes before performing log rotation
+#comment it to disable log rotation
+".to_string(),
+	);
+
 	retval
 }