Push nil if a player start is NULL
Make lib_teamstartslen push numteams - 1 instead of MAXTEAMS

Refactor player starts

Add G_GetBestPerformingTeam, G_GetWorstPerformingTeam, G_GetMostAdvantagedTeam, and G_GetMostDisadvantagedTeam

Make other fixes

Make UDMF scale compatible with ZDoom's spec

See merge request STJr/SRB2!2086

Total score starts at record score

See merge request STJr/SRB2!2091

Improved version checks for demo file lists

See merge request STJr/SRB2!2095

No longer relies on the demoversion global variable (which was incorrect for a couple instances, like ghosts), now we pass the version to the file list functions. Also don't set any demo global variables when checking a demo for valid files before playback. Also also, exit said file check function asap if its a title demo instead of doing it after we've already opened the file.