Object Versioning: object table instead of property table

not all property access via proxy redirected to global property table,
but instead objects with properties, where properties might be primitive
objects or alias objects and access to alias objects is redirected to a
global object table
Object Versioning: made proxies fully virtual

a proxy has an id that resolves to an actual object via a global
object table where the actual object is different for different
versions of such object tables. therefore a proxy should refer to
any of those target objects...
Object Versioning: fixed the simple linear global undo+redo