Sort by Level does not keep sorting after song completion on songs with multiple difficulties

[Morillus]

When sorting by level and playing a song that has multiple difficulties, the sorting does not retain after the song has been completed (or exited).

For example, I sort by 11's and select a song that has 4, 7, 10 and 11 difficulties. Upon playing the song, the sorting has now reverted to the easiest difficulty of the song and is now sorting by 4's. To play another 11, I'd have to close the 4 folder and go back into the 11 folder to select it. It seems that the behaviour is for it to revert to the easiest difficulty of the song and thus if a song only has one difficulty, it does not break sorting.

In addition, the difficulty does not automatically change on a song when sorting by difficulty. Using the previous example, if I then decided to play the 4 level difficulty of that song and then sorted by 11's, I would then have to select the 11 difficulty of the song as the difficulty would still be set to 4 (even though we are now sorting by 11). This should automatically change when you sort by difficulty.

The "Digital Dance" theme uses a custom LUA songwheel that is able to accomplish level sorting correctly, so perhaps that would be a good basis to check in order to fix this.

[stclairdaniel]

I am not sure if this is ITGMania or SL, but potential dupe of https://github.com/itgmania/itgmania/issues/181