Add a !purge command

[mikeyaworski]

• Following #3, this command should be disabled by default and only the owner of a discord should be able to enable purge.

• Should be able to purge all of your own messages

• Required to provide a mention of yourself to confirm that you are purging yourself (in addition to the confirmation reaction on the confirmation message)

• Accept two message arguments that specify a range

• Accept a channel message argument that specifies a channel to delete (in addition to the message arguments). Only the OWNER should be able to purge a channel.

[mikeyaworski]

For confirmation, we can do something like what Carl does:

[mikeyaworski]

Added ConfirmationCommand here: 132833470e3e99498949c9c350630cdda99b70d9

[mikeyaworski]

Note the similarity between !purge and !delete. The only difference is that !purge allows you to specify a user/channel to purge. We can try to merge them into the same command, but based on the nature of the optional arguments, it might be easiest to keep them as two separate commands. To merge them, we would have to manually parse the args, rather than using the value that Commando brings to us.

!delete is for message ranges within the channel. !purge is for purging a channel or user (optionally within some message range). But purge a user/channel; delete messages.

!purge <user | channel> [channel] [startMessage] [endMessage]

So then

!purge @someUser
!purge @someUser #in-some-channel
!purge @someUser #in-some-channel from-here to-here
!purge #some-channel