New capabilities for accessing KIM portable models parameters

Add an ability within LAMMPS for getting/setting KIM
portable models (PM) parameters. The assumption is that
the model is already known (through 'kim_init') when
calling the new command.

'kim_param get' gets the value of PM parameters, where
the command input includes:
parameter name, & location, or indices range, and the
variable(s) name / variable name + split / list /explicit
to return the value(s).

'kim_param get paramname index_range varname [s|split|list|explicit]'

'kim_param set' sets the value(s) of PM parameters, where
the command input includes:
parameter name, & location, or indices range, and the
corresponding variable(s) value(s).

'kim_param set paramname index_range value(s)'

NOTE: The varable_name is the name of the lammps variable in the
lammps input script and can be used in other locations in the
script.