Add commands for quoting messages

[emmiegit]

Similar to !message but affords itself to easier quoting of ranges of messages, and spends minimal space on informational aspects of the message (when it was edited), but rather focuses on copying a previous conversation into a new channel.

• Accepts jump links in addition to message IDs (see #108)
• Outputs a jump link to the first message
• Copies user avatars and names as they were during the conversation
• Has a non-intrusive visual display for edited/deleted messages