updates "add eco df"

We think we followed all your requests/advice/suggestions (thanks!). We were unable to compile the current master (!) on Ubuntu and MacOS unless we added -std=c++11 to the Makefile(s) compiler flags. Note that this is NOT related to this pull request / the ECO Force. With  this compiler flag, the current master works well with the fix_orient_eco (now renamed). The fix has been moved to USER-MISC (but we hope to get it to MISC later). We can't "make style_check ", but we have added our command to commands_fix.rst. We don't know GitHub well enough, so we don't know how to make sure that the PR #2122 was already included in the master, which we downloaded today.

examples/USER/misc/orient_eco/orient_eco.in

@@ -0,0 +1,17 @@
+log log.orient_eco
+dimension 3
+boundary p p p
+units metal
+atom_style atomic
+read_data examples/USER/misc/orient_eco/sigma5.lammps
+pair_style eam
+pair_coeff * * potentials/Ni_u3.eam
+timestep 0.001
+fix integrator all npt temp 750 750 0.1 iso 0 0 0.1
+fix eco all orient/eco 0.08 0.25 3.6 examples/USER/misc/orient_eco/sigma5.ori
+thermo 100
+thermo_style custom step temp etotal press vol f_eco
+velocity all create 750 1
+dump save all custom 100 orient_eco.dump xs ys zs f_eco[1] f_eco[2]
+dump_modify save sort id
+run 1000

examples/USER/misc/orient_eco/sigma5.ori

@@ -0,0 +1,6 @@
+1.671685 0.557228 1.76212
+0.557228 -1.671685 1.76212
+2.228913 -1.114456 0.000000
+0.557228 1.671685 1.76212
+1.671685 -0.557228 1.76212
+2.228913 1.114456 0.000000