twzCronChart: Parse crontab schedule and generate Gantt charts

This class can be used to parse crontab schedule and generate Gantt charts.

It can parse a list of scheduled tasks given as a string in the crontab format.

The class can display a Gantt chart in a Web page to display the schedule of tasks for a given period.

It can also return several types of information about the scheduled tasks like the number of cron tasks, the cron line for each task, and the next and the last date of a task.