Add hint for OR'ing TERMs to help text for ls/list.

The regexp syntax and quoting rules aren't known to many who are not well versed in the Bash shell, and difficult to get right even for people in the know. This question came up just recently on the mailing list, too.

todo.sh

@@ -199,7 +199,10 @@ help()
 		    list [TERM...]
 		    ls [TERM...]
 		      Displays all tasks that contain TERM(s) sorted by priority with line
-		      numbers.  If no TERM specified, lists entire todo.txt.
+		      numbers.  Each task must match all TERMs (logical AND); to display
+		      tasks that contain any TERM (logical OR), use
+		      "TERM1\|TERM2\|..." (with quotes), or TERM1\\\|TERM2 (unquoted).
+		      If no TERM specified, lists entire todo.txt.
 
 		    listall [TERM...]
 		    lsa [TERM...]
@@ -215,7 +218,7 @@ help()
 		    lf [SRC [TERM...]]
 		      Displays all the lines in SRC file located in the todo.txt directory,
 		      sorted by priority with line numbers.  If TERM specified, lists
-		      all lines that contain TERM in SRC file.
+		      all lines that contain TERM(s) in SRC file.
 		      Without any arguments, the names of all text files in the todo.txt
 		      directory are listed.
 
@@ -223,7 +226,7 @@ help()
 		    lsp [PRIORITY] [TERM...]
 		      Displays all tasks prioritized PRIORITY.
 		      If no PRIORITY specified, lists all prioritized tasks.
-		      If TERM specified, lists only prioritized tasks that contain TERM.
+		      If TERM specified, lists only prioritized tasks that contain TERM(s).
 
 		    listproj
 		    lsprj