Use extender class for logging WP core events

[In the meantime](https://github.com/bonny/WordPress-Simple-History/issues/16) Simple_History_Extend class was renamed to Simple_History_Module as the base class, including changed hook names. Also some new events are added, like plugin install/update/delete, theme install/update/switch/delete and more. Most importantly, event strings are now better setup for i18n, instead of concatenating strings to form sentences. Additionallly proper inline phpdoc documentation of all events/functions is introduced and event documentations states the used hooks.

Note that some hooks fire simultaneously (edit post + change post status + change revision etc.), so this code isn't yet ready for launch.

Note also that modules/core.php contains all core events yet. When accepted, we can split it into smaller parts of grouped events (comment, menu, plugin, theme etc.).