                              NODES MENU

  The node menu can also be invoked by pressing Alt-n.

  A position (or node) can be stored in Register 1 by clicking the 
  left mouse button over it. Register 1 can be cleared using the 
  'clear register 1' button.

  Add node: 
	Display a node. If there is a position in Register 1, it will
	be proposed as the position of the new node.
	Shortcut: Click on the left mouse button twice over a canvas
	position.

  Modify node:
	Modify a node (change its coordinates, weight, labels, outline,
	radius). If any of the coordinates is deleted, the node will
	be deleted. If there is a node in Register 1, it will be 
	proposed for modification.

  Move node:
	Choose new coordinates for a node. If there is a node in 
	Register 1, it will be proposed for moving. 
	Shortcut: Click on a node with the middle mouse button and
	drag the node with the button pressed.

  Raise node:
	Raise a node above all the other nodes on the display (i.e., 
	the node will not be covered by other nodes). If there is a node
	in Register 1, it will be proposed to be raised.
	Shortcut: Click on a node with the left mouse button and press 'r'.

  Lower node:
	Lower a node below all the other nodes on the display (i.e., 
	the node will not cover other nodes). If there is a node in 
	Register 1, it will be proposed to be lowered.
	Shortcut: Click on a node with the left mouse button and press 'l'.

  Node info:
	Display information about a node, e.g., its coordinates, weight,
	label, outline, radius; its degree and the edges adjacent to it.
	If there is a node in Register 1, it will be proposed.
	Shortcut: Click on a node with the left mouse button and press '?'.

  Delete node:
	Delete a node. All the edges adjacent to the node will be deleted
	also. If there is a node in Register 1, it will be proposed for
	deletion.
	Shortcut: Click on the node with the left mouse button and press 'd'.
