Name:
  Command

Intent:
  - allow operations on commands such as undoing or redoing or sequencing

Structure:
  - commands are abstracted as data (objects)
  - there is a interface for commands, has methods
       - execute
       - undo
       - redo
  - there has to be a history
  - invoker (manager) calls execute
  - receiver (subject) undergoes the action

Notes:
  - beware of undo and undo
  - there should be a class for metacommands