Renamed two functions in FileIO API to a clearer name.
Changed getAddonsDir to getAddonDir. Also rename function calls in various addon lua files.
Added classes FileReader and FileWriter.

FileIO class was getting bloated and needed to be split up. These changes will hopefully address it.
Initial fixes for new API.
Made html addon use new API.
Made json addon use new API.
Removed old FileAPI class and references to it.