logic error fix, x_L was defined twice and x_U wasn't specified at all
nonlinear solver portion is using gene_expr for 'v dot g'
Added NonlinearSolver to grasp JIpopt
FBA calculates successfully
"mumps_mem_percent" possibly fatal error, added placeholder to adjust memory requirements

documentation: http://www.coin-or.org/Ipopt/documentation/node59.html