Introducing GMAO ODAS obs sources

[Dooruk]

First tests with ODAS observations, still adding more. Showing scatter plots for ARGO data jedi vs h(x) salinity and temperature (black dots failed the QC):

Salinity	Temperature

FYI @DavidSRussell, you should be able to test with these YAMLs (by setting odas as the obs provider) and in theory it should be easy to add SWOT altimeter data to the list.

• Filters in YAMLs need to be modified according to our needs, @lren20 can help with this part.
• One caveat with current R2D2v1 implementation is that only one provider can be chosed (e.g., for marine odas or geos_marine)
• VarBC handling requires further thinking, in particular pertaining how JEDI handles empty obs files while the obs. YAMLs contain VarBC entries.

[rtodling]

Quite nice!!!