Feature get agent weights

fixes #44 -- creates a weight file for each agent during model initialization and uses the weight file (denoted by a 6 digit number representing the agent ID) on each lens update call

fixes #24 -- b57e27cb007c445f0af91f40cbadadbb8acd5238

fixes #23 -- files location are not saved via a parameter in the mail.py file there are still some hard coded directories, that still need to be worked out though, but the outputs are in separate folders (at least the weights and model output are; lens files used during model run are still output in the current working directory)

fixes #18