4. Pass polarisation info to the C/GPU code

[JLBLine]

First of all, have to edit _components_t to include

• rm_values
• linpol_frac
• intr_pol_angle
• linpol_comp_inds
• linpol_zero_I_comp_inds
• Vpol_frac
• Vpol_frac_comp_inds
• V_power_SIs
• V_curve_SIs
• V_curve_qs
• V_power_comp_inds
• V_curve_comp_inds

Maybe rename the assumed Stokes I arrays to be clear:

• power_SIs to I_power_SIs
• curve_SIs to I_curve_SIs
• curve_qs to I_curve_qs
• power_comp_inds to I_power_comp_inds
• curve_comp_inds to I_curve_comp_inds

At the same time, we should delete:

• power_ref_stokesQ
• power_ref_stokesU
• curve_ref_stokesQ
• curve_ref_stokesU

as these are wrong and should never have existed. I imagine we'll need to add something like the following to _source_t:

• n_linpol
• n_V_polfracs
• n_V_point_powers
• n_V_point_powers
• n_V_point_curves
• n_V_gauss_powers
• n_V_gauss_curves
• n_V_shape_powers
• n_V_shape_curves

Will then have to edit source_components::copy_chunked_source_to_GPU and source_components::copy_chunked_components_to_GPU to copy across these new fields.

Testing - this function will be tested when testing all the different polarisation options.

[JLBLine]

Added this in 43c08b56447ecd65e620492b290b52eb37cb4178, and fixed old tests that it breaks. Will get tested further down the line with other functions being tested