Add message command versions of existing slash commands

[Alan19]

This would involve turning a bunch of slash commands into hybrid commands, and adding parameters to existing hybrid commands

• Allow specifying of dice kept (probably want to do this in statistics too) (Dice kept in message commands + prevent other people from enhancing your own rolls #104)
• Allow user to tell bot to send statistics directly to channel #106
• Make text command version of /language #107
• Make text command version of /damage #108
• Update documentation of ~d ~p #110