[critical] Data loss when selecting BMS versions on main screen listbox; and this happens non-predictably

[arithex]

1- modify some bindings
2- go back to home "Launcher" screen
3- select another BMS version (purposeful or accidental)
4- restore selection to the previous version

Observed: none of our changes were saved
Expected: our changes are saved

Making this worse: depending on how the startup codepath goes (probing the registry and saved-prefs file for last selection).. the listbox may not have an initial selection at all -- when you go to actually save/exit or launch BMS, the selection-change event kicks in, and you lose all your recent changes.

[arithex]

Note this is not a regression for U3.. AL 2.2-2.3 seems to suffer from this problem.

Pretty sure I've seen this happen, but was never able to repro because of the winding codepaths on startup...

[arithex]

Fixed in #112