Document shouldn't be considered as modified after reverting changes with "Undo"

Scenario 1:

1. Open an alignment that can be edited (e.g. "COI.aln").
2. Modify the alignment (e.g. insert a gap).
   Expected result: the "Undo" button is enabled. In the Project View the document and its object have blue font.
3. Click the "Undo" button.
   Expected result: the "Undo" button is disabled, the "Redo" button is enabled. In the Project View the document and its object have black font again.
   Actual result: the buttons states are the same.
4. In the Project View select the document and click "Remove selected items" in the context menu.
   Expected result: the document is removed.
   Actual result: a message box is shown that asks, if the document should be saved or not.

Scenario 2:

1. Open an alignment that can be edited (e.g. "COI.aln").
2. Modify the alignment (e.g. insert a gap).
   Expected result: the "Undo" button is enabled. In the Project View the document and its object have blue font.
3. Click the "Undo" button.
   Expected result: the "Undo" button is disabled, the "Redo" button is enabled. In the Project View the document and its object have black font again.
4. Click the "Redo" button.
   Expected result: the "Undo" button is enabled, the "Redo" button is disabled. In the Project View the document and its object have blue font.

Similar scenarios should be tested for Sanger Reads Editor as well.