[epub] Replace html entities by right utf-8 code of articles before writing them in chapter.
[epub] When we save settings we come back to epub settings
[epub] Update PHPEpub library to revision 3.20
[epub] Add hooks only when user is connected (fixes Idleman/Leed-market/issues/79 #79)

(update function names to be more explicit)
[epub] Replace tabulations with spaces
[epub] Remove unused arguments to avoid error on them
[epub] Update revision number