Make AlmArray encapsulate the pyopencl Array object

Closes #59

See merge request !32

We are not testing scipy here, so if scipy produces bad output then
that test case should be skipped and hypothesis should try a new one.

Subclassing caused problems when the Array code tried to create
another Array object using `self.__class__`.

Resolve "Update package metadata for PyPI"

Closes #55

See merge request !31

Resolve "Do not require Fortran compiler / f2py for Wigner 3j symbols"

Closes #38

See merge request !29

Do not remove the wignerSymbols.f source file as this will still
be useful for the C/Fortran bindings - see #14

N.B. Python parses
    -1 ** x
as
    -(1 ** x)

These numbers are the Gaunt coefficients, multiplied by a factor of
sqrt((2 * l_3 + 1) / (4 * pi))

Merge branch '15-change-ylm-representation-to-store-magnitude-and-exp-i-phi-separately' into 'master'

Resolve "Change Ylm representation to store magnitude and exp(i*phi) separately"

Closes #15

See merge request !28

Resolve "Add SPDX / fsfe-reuse metadata"

Closes #51

See merge request !30

Yes, the LGPL is a silly licence to use for a README but since it
contains EMBL-copyrighted material I can't do anything else.

TODO: Rewrite the README so it can be CC-BY.

This code was taken from:
https://github.com/joeydumont/wignerSymbols/blob/master/src/wignerSymbols-fortran.f

Copyright ownership is EMBL for the time that I was working there,
and Christopher Kerr thereafter.

These files were written after leaving EMBL so I am the sole copyright owner.