Save bans and ban context to a database and make them searchable

[Xetera]

Ban context can include the following:

• Banned member's total time in server until ban
• Banning moderator
• Ban date
• Guild size at the time
• The banned person's last X messages before ban (5 sounds like a nice number, could be higher for premium perhaps), messages should include:
  • Content, obviously
  • Send date
  • Channel

As much as I would love to include total message count in server in here, that's just not possible with bots (yet).