Update logger config options

Architecture.md

@@ -27,7 +27,10 @@ file-manager:
     cache:  # only in case that there is cache module
         cache-dir: "/tmp/cache"
 logger:
-    file: "log.txt"
+    file: "/var/log/worker"  # w/o suffix - actual names will be worker.log, worker.1.log, ...
+    level: "debug"  # level of logging - one of "debug", "warn", "emerg"
+    max-size: 1048576  # 1 MB; max size of file before log rotation
+    rotations: 3  # number of rotations kept
 limits:
     time: 5  # in secs
     wall-time: 6  # seconds