New Gantt chart improvements

Before retiring the old flash Gantt - the functionality in the new Gantt needs to at least match the old Gannt. Including:

- have the same functionality you do in task view as you do in Task view w/ Gantt chart open. Specific example: when I go to instead the duration on a task while in Gantt view (with edit on) - I can't edit it in the column. But I can expand the task in the Gantt view. I should be able to do both.

- Static date/header: If my page has too many tasks, I scroll down and I lose the context of what date I'm seeing in the Gantt view