Make input file name to pyFANS configurable

[IshaanDesai]

Currently the input file name in pyFANS is hard-coded as input.json in the header:

FANS/pyfans/micro.hpp

Line 21 in 3c68150

MicroSimulation(int sim_id, char *input_file = "input.json");

This can be made configurable by modifying the Micro Manager API to pass in a configuration file name.