ECM_BELOW_THRESHOLD - Helper function for enzyme cost minimization
SYNOPSIS
function [ineq_constraints, eq_constraints] = ecm_below_threshold(ecm_score,xx,pp,u_threshold,x_min,x_max,ecm_options)
DESCRIPTION
ECM_BELOW_THRESHOLD - Helper function for enzyme cost minimization
function [ineq_constraints, eq_constraints] = ecm_below_threshold(ecm_score,xx,pp,u_threshold,x_min,x_max,ecm_options)