use max iterations also in the low-scale model
do not make the whole utility classes templates, only some functions
use the same runner for a low-energy model as in the GUT-model case

Todo: We need to create a susy-scale constraint which sets all (other)
model parameters from the SLHA input file.  "Other" parameters means all
parameters, except

 * the ones set at the low scale (gauge, Yukawa, LowScaleInput)

 * the ones fixed by the EWSB equations