eeshow/TOOD: add help, location string (for collaborative viewing)

eeshow/TODO

@@ -45,6 +45,11 @@ GUI:
 - highlight nets ?
 - we use find_corresponding_sheet way too often. Consider changing curr_sheet
   to new_sheet and old_sheet.
+- help screen: maybe render with Pango markup in new window (toggle window
+  creation / destruction with h/?), using Gtk to scrolling and such.
+- introduce location string, as command-line argument, e.g.,
+  [top-sheet/]rev-old,rev-new[,x,y[,zoom]]
+- set/use location string via clipboard
 
 GUI/history
 - should have quick way to show diff of a single commit