Removed output_itemized_energy(), added compute pair support

{ecoul}.  The output of these quantities is controlled by the

"thermo"_thermo.html command.

This pair style also tallies a breakdown of the total ReaxFF potential

energy into sub-categories, which can be accessed via the

"pair compute style"_compute_pair.html command. The 14 entries

in the vector generated by the compute pair command correspond

to the following sub-categories (the variable names in italics match those

used in the ReaxFF FORTRAN library): 

{eb} = bond energy

{ea} = atom energy

{elp} = lone-pair energy

{emol} = molecule energy (always 0.0)

{ev} = valence angle energy

{epen} = double-bond valence angle penalty

{ecoa} = valence angle conjugation energy

{ehb} = hydrogen bond energy

{et} = torsion energy

{eco} = conjugation energy 

{ew} = van der Waals energy

{ep} = Coulomb energy

{efi} = electric field energy (always 0.0)

{eqeq} = charge equilibration energy :ol

In order to print these quantities to the log file (with descriptive

column headings) the following LAMMPS commands can be 

included in the input script:

compute reax all pair reax

variable eb  	 equal c_reax\[1\]

variable ea  	 equal c_reax\[2\] 

 \:

variable eqeq 	 equal c_reax\[14\]

thermo_style custom step temp epair v_eb v_ea ... v_eqeq :pre

Only a single pair_coeff command is used with the {reax} style which

specifies a ReaxFF potential file with parameters for all needed

elements.  These are mapped to LAMMPS atom types by specifying N