Added optional arguments and flat resonant scattering XS to SLBW
Merge branch 'master' of https://github.com/wbinventor/PINSPEC

Conflicts:
	sample-input/Infinite_MC_Statistics/absorption rate_test.txt
	sample-input/Infinite_MC_Statistics/total flux_test.txt
	sample-input/infinite.py
	xs-lib/U-238-capture.txt
Trying to merge
Merge branch 'master' of https://github.com/wbinventor/PINSPEC