- Documentation
- Memory leaks solved

Changes to come:
-Exchange interaction computation to check (loop on neighbors),
-Temperature/random fluctuations to correct (effects too strong),
-Physical results to check,
-Add final interactions (DMI, ME, Dipolar),
-Compute spin temperature (Nurdin and Ma formslisms),
-Work on MPI parallelization,
-Ewald sums to implement (see with Stan's pakage),
-See for prefered magnetic axis (Mitchell's idea),

suggested by felipe perez in https://sourceforge.net/p/lammps/mailman/message/36236631/

rather than placing an if statement around every incidence of calling atom->check_mass() to ensure it is only called when per atom masses are not set, we place that check _inside_ Atom::check_mass(). This avoids unexpected error messages.

changes for next patch, 2d disc options for spheres, fix external upgrade, bug fixes for fix ave/chunk for density calcs, Aidan doc page citation deconvolution

NOTE: pair evaluation order changes, causing numerical differences!
Atom pair processing order is fully planned out in npair_half_bin_newton_ssa
Makes the SSA neighbor list structure very different. Do not use by others!
Each local is in ilist, numneigh, and firstneigh four times instead of once.

Changes LAMMPS core code that had been previously changed for USER-DPD/SSA:
Removes ssaAIR[] from class Atom as it is now unused.
Removes ndxAIR_ssa[] from class NeighList as it is now unused.
Increases length of ilist[], numneigh[], and firstneigh[] if SSA flag set.

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@15561 f3b2605a-c512-4ea7-a41b-209d697bcdaa

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@15527 f3b2605a-c512-4ea7-a41b-209d697bcdaa

(cherry picked from commit f7e741f3443964b7fd39e3e88817dc9f00108bb3)

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@15468 f3b2605a-c512-4ea7-a41b-209d697bcdaa

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@15203 f3b2605a-c512-4ea7-a41b-209d697bcdaa

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@15185 f3b2605a-c512-4ea7-a41b-209d697bcdaa

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@15080 f3b2605a-c512-4ea7-a41b-209d697bcdaa