TotalRate keyword is ignored in generating .net, SBML, and other outputs

[jrfaeder]

For compatibility with NFsim, the TotalRate keyword is allowed in reaction rules and is written to BNGXML files and correctly parsed/interpreted by NFsim. However, it is not written to the .net files used by the internal simulators or other output formats, including SBML, C, and Matlab.

begin model
begin parameters
  k 1
end parameters
begin species
  A() 1000
end species
begin observables
  Molecules A A()
end observables
begin reaction rules
  A() -> 0 k*A TotalRate
end reaction rules
end model
generate_network({overwrite=>1})
writeSBML()
writeMfile()
simulate({method=>"ssa",t_end=>10,n_steps=>100})