Display tasks in a gantt diagram

[snazare]

Please implement a new macro with the following parameters:

• timeframe
• projects
• assignees

that displays tasks in a gantt chart considering the added filters.

Implement a new optional task field: start date. If start date is not set but the gantt macro is used, use the creation date as start date.

[snazare]

further details:

if tasks are modified in the gantt ui, start date and due date are modified

if start date is not filled in, use creation date. If task is modified in the gantt ui, modify start date and due date.

if due date is not filled in, show task in gantt ui with a default 1w duration and show a warning "No due date set". If user interacts with the task in the gantt ui, update due date and remove warning.

add parameter in gantt macro to show or not tasks without a due date.

add parameter for space. if space is not specified, take tasks from the whole wiki.

show progress on task in gantt ui when user interacts with the progress bar.