The SLSQP solver (from nloptr) sometimes will return NaN for the parameters during
the optimization phase. Added a stop clause else it may crash the process (due
to RTMB eigen crashing).
Added a solver control function (issm_control)
tsissm 1.0.1
Initial CRAN submission based on complete re-write of model on github which was
originally created on 2020-09-16.