[Feature request] Force one-to-one sync

[oblitzitate]

If I have lots of text and audio parts (e.g. 27) and I sync them all together at once, it causes a lot of out of sync and skipping issues.

But when I sync them one at a time then combine the smil results afterwards, it doesn't seem to cause much issues, if any.

Would be nice to have an option to force one-to-one syncing.

[dhouck]

This could also be a workaround for #11 (aka r4victor/afaligner#2 and r4victor/afaligner#9)