RT minor updates
This merge request contains minor updates for the current RT schemes:
- added function prototypes for (s)part_has_no_neighbours
- added function prototype for rt_clean(rt_props)
- allow to run with any star model
- added task category RT so
scheduler_report_task_times
reports RT separately from "others"
This MR is based upon !1323 (merged) and shouldn't be looked at before !1323 (merged) is accepted - hence the WIP status for now.
Edited by Mladen Ivkovic