New PHOENIX file format

[ahmed-f-alrefaie]

Considering the older site now doesnt exist anymore. We need to implement a new loader to load in PHOENIX from different files and formats.

Example here: https://archive.stsci.edu/hlsps/reference-atlases/cdbs/grid/phoenix/phoenixm00/

[gordonyip427]

while we are on this - i think we should also consider using the phoenix files from Exotethys - so that we can be consistent with other modules too.

[ahmed-f-alrefaie]

Suggested new formats:

• Exothethys - Phoenix 2012-2013
• Phoenix -BTSettl (SVO2)
• Phoenix - Husser 2013
• Sphinx
• Castelli-Kuruz
• Atlas/MPS-Atlas
• Stagger (3D)