Fixing Support for an Empty Gantt

1) Adding on-column-click event which includes the start and end date on the event (so you can create a new event for the specified "cell"). This required adding endDate to all columns. Also created column class for consistency
2) Adding fromDate and endDate attributes to specify the minimum size of the chart. Previously if it no tasks the gantt was not visible. At this point this does not cut off events past the from or the to just ensures that the from and to dates are visible