Add optional translation config

[PintTheDragon]

Adding the ability to translate messages can be very helpful to a lot of plugins, but will clutter up the config significantly. This is why I propose there be a separate config for translations, that plugins are not required to use. Before, I'd like to define what might go inside of the translation config, and what can be left out of it:

Messages used inside of plugins should go inside of the translation config. These messages help certain plugin features, but are not a feature themselves.
Custom broadcast/hint messages should be inside of the plugin config. These exist as plugin features on their own, and shouldn't be with the other translations. There are very few of these types of messages, so they won't clutter the config and won't get mixed up with the other translations.

Translations can be implemented as follows:

IPlugin/Plugin is given a new property, of type ITranslation, which is default to null.
A new interface called ITranslation, similar to IConfig is created, although it does not include is_enabled.
Where the config manager loads configs, it also loads translations from a separate translations file, ignoring plugins that have null translations.

This should be an easy-to-implement feature, as most of what is required already exists in the config manager, and will make translating plugins much easier.

[iRebbok]

What kind of messages should plugins use from the translation config if not custom broadcasts? Log.Warn/Log.Error?

[joker-119]

It'd basically be any language localization options the plugin dev wants to support, such as changing broadcasts/hints, console messages, etc.

[PintTheDragon]

Not sure why this issue didn't close automatically when the PR got merged.