1. Fixed MAGN-190 (Crash on undoing an action that deleted two nodes with a connection)
2. Undo and redo operations are now done in the exact reversed order
3. Introduced new test case "TestDeletionsUndoRedo" to ensure simultaneous model deletion can be undone/redone correctly
Merge branch 'master' into MAGN190
Merge pull request #501 from Benglin/MAGN190

Fix for critical defect MAGN-190