Add-on API 3.1.2

Fixed util.h's dynamicStack copy method
Change tabs to spaces in headers.
Added 4 functions in util namespace.
Added expChecker.h for exported functions validations. (Much easier and
able tell developers if the functions are incorrect. NOTE: This has to
be done at END of the add-on's main file!)
Added struct_tags.h (NOTE: This is a draft process!)