OP now takes an optional list of invasion pressures (inv_points=[list of presssures])
- If inv_points is given, the npts argument is ignored
- if inv_points is NOT given, then a list of N points is generated spanning the size range in the 'capillary_pressure' array.
Trying to get OP working
Merge branch 'develop' into feature/better_props
Fixed stupid bug and typo in OP_1
Merge branch 'develop' into feature/better_props
Fine tuning
- got James/Jackie throat_conductance function working
Added late_pore_filling to multiphase.  Created a late_throat_filling too but not implemented yet.