Remove `class-plugin.php`

[simonwheatley]

Most classes in Babble extend Babble_Plugin purely to use it's helper functions. Instead we should use core functions and APIs directly, and remove the Babble_Plugin class completely.

Steps:

• [x] Convert all $this->add_[action|filter] calls to add_[action|filter]
• [x] Remove methods add_action and add_filter from Babble_Plugin
• [x] Identify other methods in Babble_Plugin used elsewhere and convert
• [ ] Convert method usage to static or, where possible/appropriate, remove and convert to core APIs
• [ ] Stop extending Babble_Plugin everywhere it's used
• [x] Profit

[simonwheatley]

See: https://github.com/Automattic/babble/pull/214

[simonwheatley]

As part of removing the plugin class, we should remove all activation and deactivation hooks.

See also https://github.com/Automattic/babble/issues/242

[johnbillion]

I think this ticket has gone about as far as it can now. PR #314 removes a whole load of unused code, and removes the Babble_Plugin dependency from most classes.

The Babble_Jobs, Babble_Languages, Babble_Switcher_Interface, and BabbleTranslationGroupTool classes use the render_admin() and get_option() methods of this class so it makes sense that it remains. The methods in the Babble_Plugin class could all be converted to static methods, but we don't gain much from this.

[simonwheatley]

Agreed, thanks @johnbillion