Reimplementation of ccdmodel according to the linkml model template

[turbomam]

Started a new clone of the linkml model template in order to use its publish to PyPI functionality. See Issue #69

Then wiped all files from this branch and copied the linkml model template based content back in. Finally added functionality from the main branch of this repo back in.

A few things to keep an eye on:

1. AUTHORS file. I'm not sure what created this or how it is used. But it's "just me" now.
2. the PyPI metadata in setup.cfg. Note that re-running MakeConfig parses model/CONFIG.yaml and might overwrite some of the files I'm mentioning here.
3. ChangeLog (generated by the Makefile?) vs CHANGELOG.md
4. taking advantage of the established mike docs practices. see esp. mkdocs.yml
5. manual edits to MAINTAINERS.md

[gaurav]

Thank you so much for all your hard work on this, @turbomam! I've removed venv entirely to avoid confusion -- everything now works through Pipenv. I had to make some fixes to sheet2linkml as well because of changes in LinkML. Finally, I made some minor edits to the Authors file (which is now AUTHORS.md), CHANGELOG, MAINTAINERS and some other documentation and configuration files. You can see all the changes I made on GitHub.

If you'd like to go ahead and merge this PR, please do so. If you disagree with any of the changes I've made, please leave me a comment. And if you'd prefer me to merge this, then I'm happy to do that too! Let me know what you'd prefer.

[gaurav]

I deliberately didn't regenerate the CRDCH model here, as I'd like to do that in another PR. But make regen-google-sheets should now be working again if you'd like to test that out or put it back into this.

[turbomam]

@gaurav I like what you've done with this PR. I have some suspicion that the documents generation & publishing or the virtual environments may need some tweaking after this merge, but I'm confident that we can easily resolve anything like that.

I think I have some verbiage about different virtual environments and the potential use of tox in the MAINTAINERS doc that could be pared down after we merge. We might be able to make the notes about initial pushes to PyPI vs subsequent pushes less convoluted, too.

[gaurav]

Thanks, @turbomam! I'll go ahead and merge this PR. I've opened an issue (https://github.com/cancerDHC/ccdhmodel/issues/103) for covering the improvements to the MAINTAINERS document you've suggested.