config: add logging config options

This commit adds config options so that users can for both the console
logger and the file logger set the following things:

- disable the logger
- omit timestamps from log lines.

sample-lnd.conf

@@ -970,6 +970,19 @@
 ; Instructs lnd to encrypt the private key using the wallet's seed.
 ; tor.encryptkey=false
 
+[logging]
+
+; Disable logging to stdout and stderror.
+; logging.console.disable=false
+
+; Don't add timestamps to logs written to stdout and stderr.
+; logging.console.no-timestamps=false
+
+; Disable logging to the standard LND log file.
+; logging.file.disable=false
+
+; Don't add timestamps to logs written to the standard LND log file.
+; logging.file.no-timestamps=false
 
 [watchtower]