Updated data-plugin replacements.
* Renamed the data-replacement function to get_data_replacements(), for better style conformance, and now calling it from the new page_depend_replacements().
* It now also returns the array of replacements, so str_replace() only needs to be called once.
* The page ID is passed in, so that this function is no longer dependant on the current page (for bookcreator's benefit).
* Some slight documentation fixes, and a .gitignore file for non-default templates.