-Disabled non custom floor backdrop setting.

-Fixed stage shadows not
being properly centered
in some L shaped rooms

-Fixed black overlay in
stage and room transitions
not scaling with screen.

-Fixed extra rooms containing persistent entities from the previous room

-Fixed Mom's Heart track not playing properly in Utero 2

-Fixed extra rooms (for example revelations' mirror room) not correctly unloading when exited by means other than a door

LevelRooms now store their ID as LevelIndex, where possible. (always for rooms generated automatically by stageapi)

Fix persistent data not being stored, PRE_STAGEAPI_SAVE_LOAD and POST_STAGEAPI_SAVE_LOAD added

SpawnFloorEffect allows you to specify a variant to switch to.

Mom and Mom's Heart now have correct fight music in Utero / Necropolis. Necropolis and Utero overlays no longer render over boss splash. Utero blood pits no longer invisible.

Necropolis & Utero override, Allow spaces in room list names in croom command if swapped for underscores, Force play stage music on entry.

Map devil/angel statue gridspawn ids to GridEntityTypes