Adding data simulation script for (CBC backgrounds)

I've created a simulation script, pygwb_simulate, that allows to simulate data for detector networks given an injection file.

Basic usage:

pygwb_simulate --observation_time {observation-time-in-seconds} --injection_file {path-to-injection_file.json} --start_time 0 --sensitivity Aplus --outdir {/path/to/output/directory} --detectors detector_1 detector_2

TODO

• Add tutorial/documentation