fixed incorrect type for Agents.add()
removed most of unit events console output to make output more readable
added needs modifiers for special needs use cases

this allows to make permanent needs never removed from the needs queue,
and needs that can satisfy multiple consumers at once

more modifiers may be added in the future
new agent type dedicated to making supply
supplies manager now dispatch suppliers MakeSupply agents

supplies building is outsourced from Supplies manager into "suppliers"
MakeSupply agents that handle needs request, ressources booking, etc
in order for one supply "provider" to be built asap
removed unused import