Add scripts for using parameter distribution

[rbiswas4]

The current available scripts for simsurvey light curve generation invoke simsurvey methods to generate a population of transients which is expected to exist in the universe, and generate observations of these transients together.

Add scripts to help decouple these, so that the user can use other methods to generate a desired population of the transients and then use simsurvey to generate observations of these transients by iterating over each transient in the population.