add cropout option to mbox importer as well
add cropout option to mbox importer as well

we have this in the archiver, makes sense to have in the importer too!

rbowen/ponymail,jimjag/ponymail,Humbedooh/ponymail,quenda/ponymail,jimjag/ponymail,rbowen/ponymail,rbowen/ponymail,Humbedooh/ponymail,quenda/ponymail,jimjag/ponymail,quenda/ponymail,Humbedooh/ponymail,jimjag/ponymail