Fix for "Align All" undo issue MAGN-275

#### Background
This commit is to fix the following defect:

MAGN-275 Align All is not recorded for Undo
http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-275

Note that "UpdateSelectionOffsets" method is also removed along with this fix. The method re-inserts the selected nodes into selection just to compute OffsetData for dragging (at a later time). This is no longer necessary as StateMachine replaced the need of OffsetData during dragging.

#### Unit Testing
Existing unit tests are passing: DynamoCoreUITests, DynamoCoreTests, DynamoMSOfficeTests, DynamoPythonTests, DSCoreNodesTests, DSCoreNodesTests.