remove attempts to use urllib and use curl for all downloading. restore printing help with no flags.

- remove cross compiler stuff
- make use of Install.py consistent
- provide options for Makefile.serial and Makefile.mpi that match those in src

Installation scripts and docs reviewed for release

Adds tutorial for using LAMMPS in Bash on Windows

Fixed typo in "compute_voronoi_atom.txt"

There was the typo "requiers" in the Restrictions section of compute_voronoi_atom.txt.

- build into local directory to replace existing installation is now default
- add wrapper function that calls curl in case python package has not ssl support
- have to specify -n flag to avoid wiping out the existing installation
- can specify -p to point to an existing kim-api installation (implies -n)

PyLammps corrections

Also fixes some regressions due to command syntax changes

restore lost KIM doc section in Section packages