Prevent malicious and rapid creation of new snapshots

[ghost]

Another possible attack vector is to rapidly create a large number of snapshots which hit the default limit of 64 which then triggers windows to remove oldest ones until all the legitimate snapshots are gone.

Possible solution could be to:
a) require signing or password when creating new snapshot
b) minimum time interval when creating snapshots
c) simple cron-like snapshot scheduler built into Raccine, requiring a password to make changes