Get rid of redundant --sync-full flag

[fcantournet]

This is a sync tool. Having the --delete flag makes sense if you want to have some kind of (partial) dry-run, but --sync-full seems redundant.

However it is "useful" right now because we suck at detecting the intent of the user from the input see #3 Once this gets solved i'll remove --full-sync and default to it.

This begs the question of having an actual --dry-run flag.