repository.BaseRepository().restore_atime() was testing in complex ways
that it only operates on a Maildir and that the 'restoreatime' setting
is set. This is unecessary, we can simply make the base implementation a
NoOp, and move the implementation to MaildirRepository().
This will save a tad of work for everyone doing IMAP<->IMAP
synchronization and simplify the code. Also document the functions.
Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>