Section Fundamental Forces corrected, all sub-sections corrected.
Some sub-sections slightly expanded for clarification purposes.
Some awkward expressrions removed, replaced or expanded.
First piece of introductory text for the Plugins/Interfaces
section. Only a somewhat long introduction of what plugins are.
TODO: discussed the 'what' of plugins, and possibly a little of
the 'why' of plugins, still require the 'how'.
