MINOR: map/acl: add the possibility to specify the version in "clear map/acl"

MINOR: map/acl: add the possibility to specify the version in "clear map/acl"

This will ease maintenance of versionned maps by allowing to clear old or
failed updates instead of the current version. Nothing was done to allow
clearing everyhing, though if there was a need for this, implementing "@all"
or something equivalent wouldn't require more than 3 lines of code.