Improve the GSP editor formatting and indentation support

The existing support for indentation and formatting in the GSP editor is somewhat below that available for other XML dialect editors. What I'd really like is for it to honor the settings in the XML editor preferences for indentation levels and breaks, and be able to bind the Correct Indentation command to a key sequence when "Editing GSP Source". Currently there is no key binding selection for "Editing GSP Source" like there is for "Editing JSP Source" and the Correct Indentation command doesn't appear to work in the GSP editor.