Combines all tasks of a project to one entry

This function is especially helpful if one wants to show a complete project only as one entry in the Gantt-chart

collapse_projects(dt, projects, task_label = "{project} collapsed")

Arguments

dt	time lines processed by calculate_time_lines
projects	that will be combined to one entry each
task_label	the label that is used for the corresonding collapsed entry

Value

dt but all entries for the provided projects are collapsed to one entry. Start and end time for the collapsed entry are the minimum and maximum start and end times of the single tasks and deadline is set to the minimum deadline (if available).