add new grid-based examples

examples/grid/in.grid.2d

@@ -0,0 +1,52 @@
+# 2d Lennard-Jones melt
+
+units		lj
+atom_style	atomic
+dimension       2
+
+lattice		sq 0.5
+region		box block 0 50 0 50 -0.5 0.5
+create_box	1 box
+create_atoms	1 box
+mass		1 1.0
+
+velocity	all create 1.44 87287 loop geom
+
+pair_style	lj/cut 2.5
+pair_coeff	1 1 1.0 1.0 2.5
+
+neighbor	0.3 bin
+neigh_modify	delay 0 every 20 check no
+
+fix		1 all nve
+fix             2 all enforce2d
+
+# load balancing
+
+comm_style      tiled
+fix             100 all balance 100 0.9 rcb
+
+# fix ave/grid
+
+fix             ave all ave/grid 10 10 100 10 10 1 vx vy
+
+# dump grid
+
+compute         ave all property/grid 10 10 1 id ix iy
+#dump            ave all grid 100 tmp.dump.2d &
+#                c_ave:grid:data[*] f_ave:grid:count f_ave:grid:data[*]
+#dump_modify     ave sort 1
+
+#dump            vtk1 all grid/vtk 100 tmp.dump1.2d.*.vtr f_ave:grid:count
+
+#dump            vtk2 all grid/vtk 100 tmp.dump2.2d.*.vtr f_ave:grid:data[2]
+
+#dump            10 all image 100 tmp.image.*.2d.png type type &
+#                zoom 1.6 grid f_ave:grid:count adiam 0.6 shiny 0.0 &
+#                subbox yes 0.01
+
+# run
+
+thermo          100
+
+run		500