Make position finalisation happen in the same phase as scenery load, i.e as a task during the main loop, instead of during the init loop. This is compatible with the existing reset logic. Unfortunately more work is needed; the environment code doesn't update the local station quickly enough on reset. (Fixing that is next!)
Modify startup sequence, so position can be modified late in the startup process, right before the scenery load starts. This allows two ugly hacks to move to a permanent, less hacky location. If other position init modes required similar late evaluation in the future, this can be accommodated now.
This is a somewhat high-risk change - I've tested both carrier starts and runway-selection based on realwx METAR, but please look out for other position-init issues and test before / after this patch.
Separate other init functions from position init, since they are unrelated, and made fg_init.cxx very complex. Next step will be brining some sanity to the position init logic :)
