Add command /move to move a range of messages to another channel.

[vxern]

The command would have an almost identical interface to /purge, with the exception of channel:

• start (String) - The ID of the start message.
• end (String) - The ID of the end message.
• authors (User(s)) - The author(s) whose messages are to be moved to another channel.
  • If unset, all messages falling into the range will be moved.
• channels (Channel(s)) - The channel(s) to move the messages to.
  • Specifying more than one channel will make Logos post the same messages into multiple channels.

Notes:

• The messages would be sent using webhooks to imitate the original user.
• Logos will lock the target channel(s) until all of the messages are moved. This is to prevent the natural flow of the messages being broken up by incoming messages.
  • TODO: Does the source channel also get locked?