Apinstall: Show a progress bar for a server job using AJAX

This class can be used to show a progress bar for a job running on the serve using AJAX to update the bar.

It displays a bar place holder section on the page that will be updated when the job progresses.

The class also generates Javascript that uses the jQuery library to send AJAX requests to retrieve the job progress status.

The class gets update notices from the PHP script running the server job and updates a file that is updated with job progress information. This information is served to the browser when it gets the job status AJAX request.