Module/Plugin system

[euantorano]

We need a module/plugin allowing easy extension of core features.

Additionally, it may make sense to make some core features into modules, such as likes. This would allow features to be easily enabled/disabled at will, and may make it easier to update and fix individual issues.

There should be an ACP area to manage modules, allowing the installation of new modules and checking whether existing modules are up to date.

Modules should be able to have the following associated components:

• View/Templates
• Styles
• JavaScript
• Settings
• Language entries
• Tasks