MOC to STC-S example, with new feature to_fits_image

[fxpineau]

Several users have asked for a S-MOC into a STC-S (or Region, ...) feature.

For another subject, Daniel Durand point me to Felix Stoehr's footprintfinder.py script.

I think we have all we need to implement the feature (at least for "small" MOCs):

• use MOC Lib Rust to_img (also used, with limited options, in MOC.display_preview) + some WCS code to create a FITS image from a MOC.
• apply Felix's script (to be checked).

Since Felix's script is ful Python, it will be a Python only feature.
What do you think @bmatthieu3, @tboch and @ManonMarchand ?

[ManonMarchand]

todo list :

• method to_fits_image (WCS code already exists in mocpy)
• see if we can use this script (GPL3) --> felix said he could re-licence to BSD3

[tboch]

@fxpineau : the overall strategy looks good to me, but Felix's script licence makes it incompatible with our code.

[fxpineau]

@tboch yes: with @ManonMarchand we looked at the license yesterday.
So far the idea would be to provide a to_fits_image method in MOCPy
and then make an example/tutorial using Felix's script.
Thus it will not be a feature implemented in MOCPy but MOCPy users will know how to do it.