LATTE package doc update and some small code changes

doc/src/Section_packages.txt

doc/src/fix_latte.txt

examples/README

examples/latte/data.sucrose_non_opt.lmp

examples/latte/in.latte.sucrose

examples/latte/log.19Sep17.latte.water.g++.1

examples/latte/log.19Sep17.latte.water.min.g++.1

lib/latte/Install.py

lib/latte/Makefile.lammps.gfortran

lib/latte/Makefile.lammps.gfortran.dev

lib/latte/Makefile.lammps.ifort

lib/latte/README

src/LATTE/Install.sh

src/LATTE/README

src/LATTE/fix_latte.cpp

src/LATTE/fix_latte.h