Reflectivity files for LLNL telescope

[Vindaar]

NOTE: 21/06/23: I need to update the files, because I realized some things about DarpanX...

This PR adds the binary reflectivity files for the LLNL telescope. These cannot be downloaded from Henke, because the LLNL telescope is a multilayer setup that consists of multilayers that vary in thickness. Henke only supports multilayers of the same thicknesses as far as I understand.

The files here instead are generated using the Python library DarpanX:

https://github.com/biswajitmb/DarpanX

and in particular using the following script:

https://github.com/jovoy/AxionElectronLimit/blob/96478e2cb662aa6166a6dae8edf004f70af37e78/tools/llnl_layer_reflectivity.nim

This is the modified version that allows changing the ranges etc. as part of this PR here:
jovoy/SolarAxionRayTracing#22

As the PR mentions the produced HDF5 file is then converted to the binary format as used by REST with the snippet mentioned over there.

The LLNL telescope further uses different coatings for different shells of the telescope, which will likely require some changes to the REST raytracer in addition to lookup the correct reflectivity value for the shell that is being hit.

For the reference about the layers and which coating is used for which layer, see the PhD thesis by A. C. Jakobsen from DTU, in particular page 62 (page 85 of the PDF):
https://backend.orbit.dtu.dk/ws/portalfiles/portal/122353510/phdthesis_for_DTU_orbit.pdf

The filenames of the added files contain the telescope shells that each file correspond to. However, this is another part where documentation about the telescope is contradictory.

The PhD thesis mentions the different coatings used for the different layers in the caption of fig. 4.12:

Figure 4.10: Optimised coatings for CAST XRT with a Pt/C material combination as calculated
by the software. The four recipes are for layer 0-3 (layer 0 is the mandrel), layer 4-7, layer 8-11 and
layer 12-14.

while the JCAP paper about the telescope (https://iopscience.iop.org/article/10.1088/1475-7516/2015/12/008/meta) contains a table (tab. 2) with the content:

| Design | Applied to layers | N | dmin | dmax |    Γ |
|--------+-------------------+---+------+------+------|
|      1 | 1–3               | 2 | 11.2 | 22.5 | 0.46 |
|      2 | 4–6               | 3 |  6.9 | 18.5 | 0.49 |
|      3 | 7–10              | 4 |  5.2 | 16.2 | 0.41 |
|      4 | 11–12             | 5 |  4.9 | 13.6 | 0.40 |

with different layers! I've used the layers given in the table for the filename, but that may need changing!

On another note: I fixed a typo in the README. It mentions 501 energies, but it's 500.
Each file is 1,802,000 bytes:
1,802,000 / 4 / 901 = 500