srmnitc/pyscal: Addition of Centrosymmetry parameter and common neighbor analysis

This release adds a number of new changes to the code: Major changes Remove pickling support Add variable conditions for clustering Add new neighbor method which finds N nearest neighbors Add centrosymmetry parameter with two algorithms Add Common Neighbor Analysis and adaptive CNA Minor changes traj process: poscar with selective dynamics can be read in add write poscar method split trajectory will automatically remove incomplete snapshots Add misc module which has methods to compare atomic environments system remove stale indicator functions restructure system code and clean up atom remove access functions and implement read_write restructure atom code and clean up faster chi params method documentation updates remove access functions and implement read writ