Document which attack steps should be used as entry points

[andrewbwm]

Document which attack steps should be used as entry points for the attacker so that modellers know which attack steps they should select when designing general scenarios.

This is something that would be nice to have in the documentation for added clarity, but is in no way crucial.

[andrewbwm]

Do this as part of the code review(#77) since we need to check and see if all of the entry points are available to the modeller.