[loading/processing efficiency] change skipping actions to be passes added via auto-actions

[michaeljb]

• abilities all list the exact steps they can be used on, should be able to make abilities() simpler and more efficient
  • steps might need a sym representation
• transition auto-skip to be auto-actions in UI; during loading, won't need to check graph for tile lays

[michaeljb]

other loading efficiency ideas

• fewer calls to actions
  • all actions include the name of the step which processed them
  • when loading games, only call actions for the entity on the action being processed, if any at all
• steps can have separate process_{action} and (pre|post)_validate_{action} methods where all errors are raised, validation could be skipped for loading