Retrieve user facing messages from JSON file

[CarrotManMatt]

Using a JSON file to store user facing messages enables the opportunity to add translations, rather the strings being hard-coded.

This should also include the activity specific error messages defined in TeXBotCog.ERROR_ACTIVITIES.

Any command descriptions/button labels should also be retrieved from this JSON file.

[sapphyree]

I agree that reading from a file is good, but the real benefit is caching, and not translations? Translations don't really make any sense for a bot used on an English Discord server.

[CarrotManMatt]

Oooh, yeah good point about caching. I wasn't planning on actually doing any translations, it just leaves the door open for future changes.

Either way, there are good reasons to do this.👍