This class provides interaction with nodes that represent Ptolemy II
relations. It provides a double click binding to edit the parameters
of the relation, and a context menu containing a command to edit parameters
("Configure"), and a command to get documentation.
Set the configuration. This is used in derived classes to
to open files (such as documentation). The configuration is
is important because it keeps track of which files are already
open and ensures that there is only one editor operating on the
file at any one time.