auto-saves every minute and recovers upon crash

auto-save time is not configurable yet. saves "recover.mmp" to
WORKING_DIR every 60 seconds. Deletes recover.mmp on successful
close of LMMS. If recover.mmp is found upon start, it loads that
project.
(cherry picked from comit f73ccadc17)
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f