Notes for XRV GUI:
------------------

DONE	o Plots like the summary plot, antisymmetric, etc should popup in a
	  separate window with a single "done" button.
	o Need help buttons on parameter popups
DONE	o popup editors for psets
	o Need to figure out Unlearn/Update/Cancel actions

UI Parameters:
   In the GUI
	fxcor	Parameter	fxcorPars

	proc fxcorPListCallback { param old new } {
	    foreach item $new {
	        switch [lindex $item 0]
	        <param> ...action [lindex $item 1]
	        ....
	    }
	} ; send fxcorPList addCallback fxcorPListCallback

    In the client
	cmd_function ()
		:
		call ui_fxcorpar ("function", value)

	procedure ui_fxcorpar (par, val)
		....generate a "{param value}"
		call gmsg (gp, "fxcorPar", param_list)

	procedure ui_fxc_update (rv)
		....generate a list of "{param value} {param value}"
		call gmsg (gp, "fxcorPList", param_list)


	The idea is that client actions such as keystroke/colon commands would
update the gui with the single value that was changed.  The entire parameter
set would be updated with a single command showing the current state of the 
client. When the parameter editor form is started an update command will be
send to fill out the form initially, a "cancel" action would also do this to
get the changes since the last "apply".  The single parameter procedure only
needs to worry about parameters that need to be known in the GUI for things
like menu bitmaps, toggle states, menu labels, etc.