change the default of the "threephase_model" parameter from "simple" to "gwseg"

Using "simple", the Norne deck aborts with an exception.

Note: SPE1 and SPE9 still seem to work fine with this but there might
be small differences so that the reference solutions of the Jenkins
server might need to be updated...
change the defaults for pvt_tab_size and sat_tab_size to -1

this causes the code to use linear instead of spline
interpolation. thanks to @atgeirr for pointing this out..
Merge pull request #649 from andlaus/change_threephase_model_default

change the default of the "threephase_model" parameter from "simple" to ...