Use a separate preferred directory for saves/exports/imports from "directory with the .bsxm"

[Adam Winer]

.bsxms are likely to be in an entirely different directory from everything else.

[Adam Winer]

Resolve Issue #467: Use a separate preferred directory for saves/exports/imports from "directory with the .bsxm"

→ <<cset f4b13d0d7741>>