Update documentation to new handling of dry-mode database

docs/bot-usage.md

@@ -45,14 +45,17 @@ optional arguments:
   -h, --help            show this help message and exit
   --db-url PATH         Override trades database URL, this is useful in custom
                         deployments (default: `sqlite:///tradesv3.sqlite` for
-                        Live Run mode, `sqlite://` for Dry Run).
+                        Live Run mode, `sqlite:///tradesv3.dryrun.sqlite` for
+                        Dry Run).
   --sd-notify           Notify systemd service manager.
   --dry-run             Enforce dry-run for trading (removes Exchange secrets
                         and simulates trades).
 
 Common arguments:
   -v, --verbose         Verbose mode (-vv for more, -vvv to get all messages).
-  --logfile FILE        Log to the file specified.
+  --logfile FILE        Log to the file specified. Special values are:
+                        'syslog', 'journald'. See the documentation for more
+                        details.
   -V, --version         show program's version number and exit
   -c PATH, --config PATH
                         Specify configuration file (default: `config.json`).
@@ -68,6 +71,7 @@ Strategy arguments:
                         Specify strategy class name which will be used by the
                         bot.
   --strategy-path PATH  Specify additional strategy lookup path.
+
 ```
 
 ### How to specify which configuration file be used?