Add to the user's guide a statement saying that the "SelectFeature" scripting command is used in the IGB Tutorial

We should make sure that we DO NOT REMOVE the "SelectFeature" command from the IGB scripting language because it is used in the IGB Tutorial.

To help us ensure that we DO NOT REMOVE this command (because we may think it is redundant due to the "Select" command) we should add a small statement in the user's guide which may really serve to help us remember that we should not remove this command.

For a description of the difference between the "Select" and "SelectFeature" commands please see the comment in IGBF-598 that clearly describes the difference between the two commands.