As a start I want to calculate the start en ending time for each bug, this is needed for the Gantt Chart.
The rule for getting the deadline/end time for each bug is
1) get target_date from mantis_plugin_ProjectManagement_target_table
if not available
2) get bug due_date or project_version date_orde, which one comes first
3) if no deadline, don't show in chart
For now the start_time for each bug can be something random.