Added hcp query example to kim_commands

The data obtained by {kim_query} commands can be used as part of the setup

or analysis phases of LAMMPS simulations. Some examples are given below.

[Define a crystal at its equilibrium lattice constant]

[Define an equilibrium fcc crystal]

kim_init         EAM_Dynamo_ErcolessiAdams_1994_Al__MO_123629422045_005 metal

boundary         p p p

For example, in the above script, the lattice command would need to be

changed to: "lattice fcc $\{a0\}*$\{_u_distance\}".

[Define an equilibrium hcp crystal]

kim_init         EAM_Dynamo_Mendelev_2007_Zr__MO_848899341753_000 metal

boundary         p p p

kim_query        latconst get_lattice_constant_hcp species=\["Zr"\] units=\["angstrom"\]

variable         a0 equal latconst_1

variable         c0 equal latconst_2

variable         c_to_a equal $\{c0\}/$\{a0\}

lattice          custom $\{a0\} a1 0.5 -0.866025 0 a2 0.5 0.866025 0 a3 0 0 $\{c_to_a\} &

                 basis 0.333333 0.666666 0.25 basis 0.666666 0.333333 0.75

... :pre

In this case the {kim_query} returns two arguments (since the hexagonal

close packed (hcp) structure has two independent lattice constants).

In the case where a query returns multiple results, the default behavior

for {kim_query} is to split these into individual variables of the form

{prefix_I}, where {prefix} is set to the the {kim_query} {variable} argument

and {I} ranges from 1 to the number of returned values. The number and order of

the returned values is determined by the type of query performed.

[Define a crystal at finite temperature accounting for thermal expansion]

kim_init         EAM_Dynamo_ErcolessiAdams_1994_Al__MO_123629422045_005 metal