extract structure tests from grammar tests
define 'HumanHasLanded' event
move grammar comments to structures' docstrings
define 'HumanWasDamagedOnGround' event
define 'HumanHasDamagedHimself' event
define 'HumanWasDamagedByHuman' event
define 'HumanHasCommittedSuicide' event
define 'HumanWasShotDownByHuman' event
define 'HumanWasShotDownByStatic' event
define 'building' grammar and 'BuildingWasDestroyedByHuman' event
define 'tree' grammar
define 'TreeWasDestroyedByHuman' event
define 'StaticWasDestroyedByHuman' event
define 'BridgeWasDestroyedByHuman' event