do mainDiagram lookup - without test T T

Undone
1. LbuttonDclk cannot get into Lookuptool unless set
DiagramEditor::Release(); but it's not reasonable...
Merge remote-tracking branch 'origin/master'

Conflicts:
	DFDEditor2/DFDEditor2/DFDEditor2/Diagram.cpp
	DFDEditor2/DFDEditor2/DFDEditor2/EditTool.cpp
	DFDEditor2/DFDEditor2/DFDEditor2/LookupTool.cpp