Control/device.js: limit the amount of logs

[jini-zh]

Button's RBU has generated over 80000 log entries, and when I click to its entry in the list of devices on the control page, the browser tab stops responding. Add something like limit 50 to the SQL query here: https://github.com/ToolDAQ/WebServer/blob/master/html-Common/Control/device.js#L80 ?

Would be nice to have some flexible and generic approach to cope with devices generating too many logs over short time.