EDITSECTIONS -- display "Edit Sections" button

• An %EDITSECTIONS% tag is replaced by an "Edit Sections" button, while disabling all the "edit" links on the headings by default.
• When the "Edit Sections" button is clicked, all the "edit" links will appear on the headings.
• Syntax: %EDITSECTIONS% or %EDITSECTIONS{"Start Editing" finish="Finish Editing"}%
• Category: EditingAndContentUpdateVariables
• Related: AutoSectionsPlugin