Expose gauss jacobi quadrature with alpha parameter

[mscroggs]

Resolves #922

[mscroggs]

@samuel0007 I've added this scaling so that the rule matches the [0,1] interval used everywhere else. Is this compatible with what you needed this for?

[samuel0007]

For my application, I only need an exposed alpha and defined on [0,1] 👍

But I think from what I understand, one should have (for general alpha and beta) - as the weight function impacts when you pullback the integral:

$$ \zeta_{i} = \frac{1 + \widehat\zeta_{i}^{(\alpha,\beta)}}{2}, \qquad \omega_{i} = \frac{\widehat\omega_{i}^{(\alpha,\beta)}}{2^{\alpha+\beta+1}}. $$

Which also match this small example I found online https://www.math.umd.edu/~petersd/460/html/gaussjacobi_ex.html

Also maybe you might also want to use this rescaled function in the make_quadrature_tetrahedron_collapsed and make_quadrature_triangle_collapsed to make it consistent?

[chrisrichardson]

I think this should go around all the explicit instantiations, e.g. if you look at get_gll_points in the generated docs, you will only see double at the moment, not T, because that was the last thing doxygen saw.

[chrisrichardson]

I guess there may be other explicit instantiations in other files... worth checking (maybe not in this PR).

[mscroggs]

I've opened #929 to remind me to do this