Improved UnitSpawner/Unit behavior control and/or events

[KiNg626]

Currently there is very limited support for customizing how a non-player force acts, making it difficult or impossible to make a force act differently to how biters act. Having more control over parameters such as default distractions, pollution responses, default commands, expansion logic, and attack responses would enable non-player forces to act as something other than just enemies to fight. It would also avoid mods needing to micro manage every spawner and unit on the map via script, especially since that requires frequent polling due to there being limited events for unit/spawner management.