Pre-flight checks

[sr229]

To be able for the bot to run properly, pre-flight checks should be done before init-ing the bot.

Pre-flight checks would check for :

• Required Tokens
• Miscellanous tokens, and disable commands that uses those tokens when undefined.

[Ovyerus]

Added in face80f, but only for core settings as the rest are optional(ish),

[sr229]

Re-opening as pre-flight should extend loading everything before connecting to Discord

[sr229]

Extending it a little :

• Check connection for redis
• Validate configuration if it exists
• lazy-load all events and modules then connect to Discord