added method for unit needs to return a UnitType
make supply changed back to cached tileposition


changes in progress to replace the ressources need reservation to avoid
attempting to make supply before having the necessary resources
new interface for producers classes

needs will now be moved from the needs manager to dedicated producer
objects that can handle resources and other requirements necessary to
fulfill a consumer's need
added convenience method to compare Units.Types to UnitType
needs refactored to contain owner Consumer object

now each Need() is assigned its corresponding Consumer in constructor
drectly