Simplied CMFD solver and fixed MOC segmentation across overlapping cells
added comments and adjusted line lengths to fit style guide
fixed PR issues
added cmfd linear algebra functions and LRA cmfd input
made minor edits for PR
fixed index error in CMFD group_indices map
made small PR modifications
added linalg.h and pairwisesum.h
Merge branch 'develop' of github.com:samuelshaner/OpenMOC into develop
merged with last commit
Resolved merge conflicts from shaner/develop