Add libraries to handle dust maps

[Zarquan]

Support request from SGoughKelly :

To be able to do some dust corrections for any Gaia stars is it
possible to add the ‘dustmaps’ package to DMP or something equivalent.
I know that the Gaia AP includes an A0 correction term but for many
stars at larger distances or large variability this is not very
reliable. This package would also allow for corrections to be made for
the crossmatched catalogues i.e 2MASS HJKs bands.

[Zarquan]

In follow up emails, SGoughKelly mentions two specific Python packages that would be useful:

• jobovy/mwdust
• gregreen/dustmaps

[Zarquan]

Duplicate of #1023, sorry

[NigelHambly]

Which one shall we close then?!

[NigelHambly]

Closing as agreed.