Expand egroups migration script to cover egroup system change ourselves

Cover egroup system change ouselves by doing:

1. Create Notification Channel with same name as egroup (with same admin and admin group) (done)
2. Allow egroup posting to this channel from that egroup (done)
3. Add corresponding Grappa group as member of the channel
4. Remove grappa sync
5. Add Notification Channel email as egroup member
6. Remove all other egroup members

when done this means: mail -> egroup -> notification channel -> grappa expansion -> members