fixed boss theme not stopping when boss is killed in custom stage api floors

fixed bug where main menu music set to a specific soundtrack late in load order could fail to load and play

- added options for main menu and nightmare tracks using repentogon callbacks
- fixed bug where mod would sometimes reset music volume to 100% regardless of users music volume setting

-fixed hush boss death check sometimes not working in repentance
-fixed womb track name not showing up in jukebox text when using the 'default' soundtrack
-increased length of 'blank' ogg file slightly just to be safe

small bug fixes

added workaround for mods with broken challenge intros

minor tweaks

-added setting into custom mode options for track to just play the floor music
-rearranged and added a bunch of code so that rooms set to use the floor music that normally have their own music by default don't restart the floor music when entering/leaving
-replaced soundtrack list shuffle ordering function with a much more efficient logic (fisher yates shuffle) game shouldn't sometimes lock up for half a second when hitting the shuffle button anymore