Add "logs" folder to logging

This is due to separating the logs from the ArcCommander's source files in the `$XDG_CONFIG_DIRS` folder.

src/ArcCommander/Program.fs

@@ -249,7 +249,7 @@ let main argv =
             |> ArcConfiguration.load
         // <-----
 
-        let arcCommanderDataFolder = IniData.createDataFolder ()
+        let arcCommanderDataFolder = Path.Combine(IniData.createDataFolder (), "logs")
         let arcDataFolder = 
             tryGetArcDataFolderPath workingDir arcCommanderDataFolder
             |> Option.defaultValue arcCommanderDataFolder