Add versioning to dml objects

[ickby]

There should be a version behaviour, allowing to make dml objects versioned. Things to consider:

Behaviour logic should be same as for transaction, with full object and sublet versioning, recursive etc.

A version should be able to consists of changes to multiple objects

If a new version contains objects that were in a version before, this new version becomes the parent or the former version

a version can have a single parent only, but multiple children

Versions should form non cyclic graphs, any cycle is an error