Check the parameter names for complex mixture models

[pkienzle]

mixtures including product models don't have the correct parameter names.

For example
`
$ sascomp cylinder+sphere@hardsphere -pars -noplot
scale: 1
background: 0.001
A_scale: 1
A_sld: 4
A_sld_solvent: 1
A_radius: 20
A_length: 400
A_theta: 60
A_phi: 60
scale: 1
sld: 1
sld_solvent: 6
radius: 50
volfraction: 0.2
`
should be:
`
$ sascomp cylinder+sphere@hardsphere -pars -noplot
scale: 1
background: 0.001
A_scale: 1
A_sld: 4
A_sld_solvent: 1
A_radius: 20
A_length: 400
A_theta: 60
A_phi: 60
B_scale: 1
B_sld: 1
B_sld_solvent: 6
B_radius: 50
B_volfraction: 0.2
`

and
`
$ sascomp cylinder+ellipsoid*sphere@hardsphere -pars -noplot
scale: 1
background: 0.001
C_scale: 1
C_sld: 4
C_sld_solvent: 1
C_radius: 20
C_length: 400
C_theta: 60
C_phi: 60
Asldradiusvolfraction_scale: 1
A_sld: 4
A_sld_solvent: 1
A_radius_polar: 20
A_radius_equatorial: 400
A_theta: 60
A_phi: 60
sld: 1
sld_solvent: 6
radius: 50
volfraction: 0.2
`
should be
`
scale: 1
background: 0.001
C_scale: 1
C_sld: 4
C_sld_solvent: 1
C_radius: 20
C_length: 400
C_theta: 60
C_phi: 60
AB_scale: 1
A_sld: 4
A_sld_solvent: 1
A_radius_polar: 20
A_radius_equatorial: 400
A_theta: 60
A_phi: 60
B_sld: 1
B_sld_solvent: 6
B_radius: 50
B_volfraction: 0.2
`
or perhaps keeping the order of the terms in the original expression
`
scale: 1
background: 0.001
A_scale: 1
A_sld: 4
A_sld_solvent: 1
A_radius: 20
A_length: 400
A_theta: 60
A_phi: 60
BC_scale: 1
B_sld: 4
B_sld_solvent: 1
B_radius_polar: 20
B_radius_equatorial: 400
B_theta: 60
B_phi: 60
C_sld: 1
C_sld_solvent: 6
C_radius: 50
C_volfraction: 0.2
`

[richardh]

temporarily move to beta(Q) project, as is related to tickets there.