Added get_subspacetime.py, a program that lets you extract subspacetimes from a *.3sx2p1 file.

	new file:   2p1-fixed-boundaries/data_analysis_scripts/get_subspacetime.py
	new file:   2p1-fixed-boundaries/data_analysis_scripts/testing_file.txt
	modified:   2p1-fixed-boundaries/high_throughput_scripts/make_post_thermalization_script_dewitt.py
	modified:   sphere_generator/state_tracking.py