Starting cleanup of ferns/

Early exit from abstract_ferns.grow_giant_tree_fern
    (very) small performance increase

Renamed "leave" to "leaf" where appropriate
Refactor abstract_ferns.grow_giant_tree_fern …
    Arguably more readable; definately more maintainable
    Potentially slower but if it is the difference would be negligable

Renamed SeTTiNGS.txt to settings.lua …
    It's a Lua file... the extension should reflect what it actually is

Stop polluting global namespace 
Bump minor version number 
Removed obsolete or useless code

Some commented code makes no sense because there is notcomment as to why it's commented out.
    Removed.