Agent Sorting

[MILeach]

This PR includes support for sorting agents which use spatial messaging by their position to accelerate message read times.

• Identify where sorting should take place
• Explore options for sorting - manual vs host API
• Automatically detect/create necessary variables
• Warning if required environment vars for sorting aren't set
• Implement sort for default state agents
• Add interface for controlling sorting frequency
• Support all agent states
• Move sort from beginning of step to most optimal point, i.e. before read takes place per agent function
• Add required method to message types to query whether sorting is required
• Visual inspection to confirm behaviour is still correct
• Add unit tests

Initial results show that the ideal sorting frequency depends on the model, both boids and circles have achieved a runtime improvement in the range of 20%-40% depending on sort frequency.

[mondus]

Suggest that each of the unit tests gives a descriptive comment to what the test is doing.

[Robadob]

I might be on the wrong page, but I think some of this needs discussion at the next meeting.

[Robadob]

I'm happy, Paul had a few comments at the meeting?