Also update the license and switch to GPL v2 like lammps

This is a squashed commit including the following changes:
1) Update mode header
2) Clean up white-space
3) Fix free variable warning
4) Add proper file ending stuff
5) Rename to keep conventional naming scheme
6) Updates to the readme
7) Update to conform to `package-lint` criteria
8) Add license header
9) Add in-file instructions

2 small bug fixes to load balancing

better rRESPA doc page, also a new Makefile.theta

Collected small updates for the next patch release

- modified the citeme reference (replaced by the JCP one)
- same modification in doc and src/SPIN

- created README in examples/SPIN
- modified doc/src/set.txt to define 'spin' and 'spin/random' keywords

update and clarify the choice of atom ids for angle style dipole (which is not really an angle potential)

fix typo in python module

couple more doc tweaks - sigh

fix glitch in ABIVERSION in fix latte

added SPIN package to Section_packages doc

Fixes issue #975

Collected small changes for the next patch release

new ARM makefiles, also some doc tweaks

Collected cmake changes

- improve error detection and messages
- avoid sigma/cutoff to be zero (and thus division by zero)
- move new/delete of temporary storage outside of loop