DFIG: Create a docked figure window

A (trivial but) convenient shortcut to create a docked figure window

DFIG works exactly as FIGURE, except that the figure is docked.

DFIG, by itself, creates a new docked figure window, and returns its handle.

DFIG(H) makes H the current figure and docks it. If Figure H does not exist, and H is an integer, a new figure is created with handle H.

DFIG is similar to DOCKF (File 12608), except that the behavior of DFIG is closer to that of FIGURE: when no argument is given, DFIG opens a new docked figure.