Modernize lsforce packaging

This MR modernizes how lsforce is packaged, by:

• Eliminating setup.py and setup.cfg in favor of pyproject.toml
• For version tracking — Removing Versioneer in favor of setuptools-scm, which requires far fewer extra files in the repo
• Package core dependencies are now stored in an environment.yml file, and developer dependencies in requirements.txt — this separates the dependency lists from the install.sh script which installs them
• The install.sh script has some minor updates to make it more robust

All of these tweaks should be more or less transparent to lsforce users, but they'll help us futureproof this repo for a bit longer.