Rollback does not work with object properties that did not exist in the old version

Steps to reproduce:

1. Create a class: Sandbox.MyClass
2. Add a property called "p1" (string)
3. Save the class
4. Create a page Sandbox.Test
5. Add an object of the class Sandbox.MyClass on it
6. Set a value to p1
7. Save the document
8. Go back to Sandbox.MyClass, add a property "p2" (a string) and save
9. Go back to Sandbox.Test, add a value to the property "p2" and save
10. Look at the history and rollback to the first version of Sandbox.Test
11. Go on edit object mode, and see: the property "p2" is still there with the value you set, even if in the version 1.1, the property did not exist.

Cause: Since "p2" did not exists in the version 1.1, the rollback action does not handle it.

It causes: XWIKI-11787.