Update LOC plot slightly.
Update LOC plot slightly.

* Improve comments
* Use markevery
* Increase markersize
* Drop average labels
* Add dashed line lightgray grid

jwpeterson/libmesh,hrittich/libmesh,capitalaslash/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,libMesh/libmesh,capitalaslash/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,dschwen/libmesh,libMesh/libmesh,capitalaslash/libmesh,hrittich/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,libMesh/libmesh,hrittich/libmesh,libMesh/libmesh,hrittich/libmesh,capitalaslash/libmesh,roystgnr/libmesh,jwpeterson/libmesh,roystgnr/libmesh,roystgnr/libmesh,capitalaslash/libmesh,dschwen/libmesh,libMesh/libmesh,roystgnr/libmesh,roystgnr/libmesh,hrittich/libmesh,dschwen/libmesh,BalticPinguin/libmesh,hrittich/libmesh,roystgnr/libmesh,dschwen/libmesh,BalticPinguin/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,dschwen/libmesh,hrittich/libmesh,jwpeterson/libmesh,libMesh/libmesh,libMesh/libmesh,hrittich/libmesh,dschwen/libmesh,libMesh/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,dschwen/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,hrittich/libmesh,capitalaslash/libmesh,roystgnr/libmesh,dschwen/libmesh