The following changes are made:
- The SurfaceComponent enum has been removed.
- Added new member Wells::number_of_phases.
- The Wells::zfrac member has been replaced with comp_frac. The old
zfrac always had 3 components per well (accessed according to the
canonical ordering given by SurfaceComponent), the new one has
number_of_phases components per well.
- Changed add_well() accordingly to accept comp_frac.
- Added new member WellControls::distr, giving distributions for
rate controls.
- All functions dealing with well controls now take Wells* and a
well index instead of directly taking WellControls*.
- Now append_well_controls() also takes a rate distribution argument.
- Added new public function set_current_control().