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 !2086

Total score starts at record score

See merge request !2091

Improved version checks for demo file lists

See merge request !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.

Means there's actually feedback for how much score you got in the current level.

Handle empty music lump name on music change

See merge request !2090