Merging `gates` into `main`

[yalinli2]

Thanks to everyone (@haclohman in particular for leading and going through the codes for each system), we are close to merging the systems in the gates branchintomain`, just want to document some changes I'd like to make before pulling those in:

• [x] Consolidate the modules, see #56
• [x] Make sure references are good, see #58
• [x] Consistent SanUnit
  • Add in required Component/ImpactItem in unit docs, see #51
  • Remove legacy comments, see #57
  • Update __init__, see #59
• [x] Make sure the units are included in tests, either through doctest or through testing the corresponding system, see #52

[yalinli2]

Just a note that this is ongoing in the private repo because of the NDA so the gates branch in the public repo is outdated now (I tried to merge, but there are simply too many conflicts now and it's much easier to make all changes in one repo rather than switching between the public & the private repo), but all units that can be public will go public when it's done

[yalinli2]

The gates branch has been merged in: #75 Note that the data sheets/references for some module still needs to be checked/updated, but those are minor and will be made to the main branch