When grouping a selection of BlElement, the order is not the same

[labordep]

Create two elements and group them.
The group contents have child but not in the same order that the selection.

[Nyan11]

Probably fix when i updated the Tree element in #110. Need testing

[Nyan11]

No it does not work

[Nyan11]

Group command memento should not create new BlElement but instead recycle previously destroyed ones.

Example: Create a group, change order of this group (on background). Use undo button until the group is remove, then use redo button until the group order is change.

An error occurs, because group Element is a new reference and it should not be.

[Nyan11]

New questions, how to test that no new reference are created by undo / redo memento ?

Add new test on test trait:

• Execute command
• Determine the context of the command (in case of group command it is the parent, in case of add command it is the added element)
• Save context
• Undo
• Redo
• Check if context is the same

[Nyan11]

#131 is merged