Corrected an error in the previous commit. Implemented a new form

of the "edit" command that takes an instance name as an argument.
This is the first of a small series of command extensions to
provide the capability to replace any command that is dependent on
the pointer position with an equivalent command that is not, for
the purpose of removing pointer and screen coordinate dependencies
from the log file created by "logcommands".

doc/html/edit.html

@@ -20,7 +20,7 @@
 
 <H2>edit</H2>
 <HR>
-Use selected cell as new edit cell
+Use selected cell as new edit cell, or specify cell to edit.
 <HR>
 
 <H3>Shortcuts:</H3>
@@ -30,12 +30,17 @@ Use selected cell as new edit cell
 
 <H3>Usage:</H3>
    <BLOCKQUOTE>
-      <B>edit</B> <BR><BR>
+      <B>edit</B> [<I>instance</I>]<BR><BR>
    </BLOCKQUOTE>
 
 <H3>Summary:</H3>
    <BLOCKQUOTE>
-      The <B>edit</B> command makes the selected cell the new edit cell.
+      With no arguments, the <B>edit</B> command makes the selected cell the
+      new edit cell.  If more than one cell is selected, then the one closest
+      to the pointer position is used. <BR><BR>
+      With argument <I>instance</I>, makes the instance named <I>instance</I>
+      the new edit cell, if <I>instance</I> exists and is in the current layout
+      window.
    </BLOCKQUOTE>
 
 <H3>Implementation Notes:</H3>