Create `/docker preset` command

[AdityaGupta1]

• Command lets user store certain "presets", or lists of commands
• Presets stored in config file
• Presets accessed by unique numbers
• Four options for argument 1:
  • (preset number) runs the preset with the number specified (arg 1)
  • get prints out the list of commands for the preset number (arg 2)
  • add adds a command (arg 2) to the preset number (arg 3)
  • remove removes command number ___ (arg 2) from preset number (arg 3)