more thoughts on rolon shapshots in the Journal

I've been thinking that there is no need for the snapshot made when a rolon is updated to contain the JU. This is needless overhead.

The CU should also not be copied in the snapshot, as it will complicate a lot of things. The CU in the snapshot will then only contain the reference to the parent of the snapshot (the transaction rolon) and pairs of links to the original rolon which was updated.