create a github repo for working on shared kernel with verified outputs, along with wrappers

[bmaranville]

Wrappers (API) requested in at least

• python
• matlab
• c++
• java

[andyfaff]

• Julia, capable of being used with Automatic Differentiation.
• pyopencl and driver
• refnx's vectorised pure Python kernel
• A C/C++ kernel used in refnx with a cython binding.

I did some rough timing investigation of the different reflectivity calculations.
<EDIT Feb2021. Resolution smearing timings now with refnx/refl1d/bornagain/genx>

[andyfaff]

I do have a Java version, but it dates from 2007.

[andyfaff]

And a rough timing comparison for resolution smearing.

<EDIT Feb2021. Resolution smearing timings now with refnx/refl1d/bornagain/genx>

[bmaranville]

Added a folder to analysis kernel.

[andyfaff]

Added a refnx folder to analysis kernel