[feature request] reduced output

[ploum]

Usecase : running offlineimap -o once or twice a day within a "do_the_internet.sh" script and be offline most of the time.

For that usecase, a reduced/summarized output would be appreciated that would display only the accounts synchronized and the folder where something was actually done (and with the number of message exchanged). If nothing, a simple "account X up-to-date, nothing to do".