Add docs for new constants

[bennibbelink]

Closes #380.

I also modified the dockerfile to no longer mamba update -y --all because it was updating libraries that cyclus depends on (specifically libicudata.so could not be found), rendering cyclus unusable. I'm not sure if we will run into trouble later on of mamba not being able to find the sphinx packages required for building the site. I think that the update command might be a remnant of using an apt build (needing to update package indexes in order to find the sphinx packages), and I'm not sure that it's necessary with conda/mamba.

[bennibbelink]

@gonuke feel free to tag some active archetype developers. I would love to hear their feedback on the docs as well but am not sure who all to bother 😄 nuclearkatie? abachma2?

[nuclearkatie]

Sorry if this is a basic question but I haven't been following this saga closely. Are the new variables able to be used in prototype declarations in input files, or only in core cyclus and archetype code bases? Like, can you declare a source with

<facility>
  <name>ExSource</name>
  <config>
    <Source
      <outcommod>commod</outcommod>
      <inventory_size>CY_LARGE_DOUBLE</inventory_size>
    </Source>
  </config
</facility>

in an input file and have it process correctly? I think either way, the docs should be clear about whether you can do this

[bennibbelink]

@nuclearkatie good question. They can be used in input files written in Python, but not XML. The latest commit clarifies this in the docs

[katyhuff]

This looks reasonable to me. I suspect the mamba issue you've fixed here might solve some installation issues one of our ARFC undergrads may be experiencing. I have no recommended edits.

[bennibbelink]

If there are no further requests for changes, can someone merge this please?