Add mockups for DM psf objects

[esheldon]

looks like its failing during the stackvana install

[esheldon]

@beckermr any ideas how to fix the stackvana install?

[beckermr]

I think this should be close to fixed. There is no need for another channel now. It is built on conda-forge.

[esheldon]

thanks!

[esheldon]

The next step is to replace SEObs with stack exposures.

• image is represented by an exposure (with variance, mask, DM psf)
• noise is also represented by exposure
• The make_sim would then return separate exposure lists for image and noise image

This is a big change

[esheldon]

This reinforces the maxim to focus on data structures and the code will fall in place.

If we had sorted out the DM data structures from the start we would not need all this code restructuring

[esheldon]

needed to add stack WCS code before making exposures

[esheldon]

I've got a temporary separate code path in the make_dmsim function (as opposed to make_sim) until I can demonstrate the new version agrees with the old, and have adapted the coadding code to use this version.

[esheldon]

currently there are some parallel versions here, e.g. the make_dmsim code that will become make_sim after more checks. But those checks must be done separately using the updated coadding code and a full run on a grid sim with PS psf

[esheldon]

More testing is needed, but it will need to be a shear recover test. we need to merge this to test further

[beckermr]

I won't get to this until next week.

[esheldon]

no problem

[esheldon]

I'm going to merge this, can you approve @beckermr ?