Small error in hwp_sys

[sgiardie]

At this line of the hwp_sys module the solver parameters are being read from file, so there should be the parameters self.h1s, self.h2s..., indicated by the final s, instead of the parameters self.h1, self.h2... without the s.

[sgiardie]

Also, inconsistency in the piece that handles the reading from parameter file when referring to self.sim.parameter_file