Add multi-select function, nodes alignment, Instruction manual

[olist] [*] Add multi-select function (select nodes by left mouse button, right mouse button and middle button can pan the window) [*] Add node alignment feature (control trick when you select multiple nodes, you need to align to which node i.e. right mouse click on this node to select alignment) [*] Add an instruction manual explaining each node in detail; [/olist]