Move from setup.py to pyproject.toml; Update build scripts

[aaraney]

Move from setup.py to pyproject.toml.
Sub-package authorship is also updated.
Build scripts are also updated.

Replaces #683.
Closes #683.

Related to:

• Make sure wheel is installed at the beginning of update_package.sh #680
• Investigate need to replace setup.py with newer configuration files #248
• Update package script fails if wheel package not installed #247

Closes #248
Closes #247

[robertbartel]

@aaraney, this look great!. I did make a few inline suggestions to add description values in some of the .toml files where it was empty. I also changed one description to remove a "MaaS" reference and replace with "DMOD," which is the only thing I think really needs to be changed.

[robertbartel]

This may not be the place to address it, but it is probably a bug that no version constraint for dmod.core is specified here (likely also true for the next line and dmod.metrics).

[aaraney]

Yeah, likely so. @christophertubbs, can you have a look at this?

[aaraney]

@robertbartel, thanks for adding package descriptions! Great teamwork!

Just added all of your suggestions, @robertbartel, and squashed them so the history is a little cleaner and rebased off of master. Can you give it a quick re-review and get this on the road?