Module Connect

This option allows modules in a data analysis graph to be connected by a
pipe that represents a flow of records between two modules.  When this
option is selected, Pablo waits for the user to click the left mouse
button on a module in the data analysis graph.  This will be the source
module.

Pablo then waits for a second module to be clicked on with the left
mouse button.  This module will be the destination of the connection.
Any records created by or copied through the source module will be input
records for the destination module.

The user may continue to connect modules, building up an entire data
analysis graph.  Clicking the right mouse button over any module will
cause Pablo to exit module connection.
