Replace dolt with nautobot_version_control

[glennmatthews]

Fixes #161.

• Move the entire dolt/ directory to nautobot_version_control/ (needed to get nautobot_version_control as the app name)
• Update models and migrations accordingly (THIS IS A BREAKING CHANGE -- you will lose any existing branches / pull requests / etc. -- highly recommend starting from a fresh database / database import after this change)
• Invoke task variables are renamed from nautobot_dolt to nautobot_version_control - update your local invoke.yml and/or environment variables accordingly
• Update GitHub Actions CI to run against Nautobot 1.2.0-beta.1 instead of 1.1.2
• Plugin name as entered in nautobot_config.py is changed from dolt to nautobot_version_control
• URLs are changed
  • /plugins/dolt/... --> /plugins/version-control/...
  • /api/plugins/dolt/... --> /api/plugins/version-control/
• Changed the author of record to Network to Code, LLC <opensource@networktocode.com>
• Plugin config now pulls version from the package version instead of hard-coding it
• Set 1.2.0-beta.1 as the minimum supported Nautobot version
• Fixed committer info for system database migrations (follow-up to #156)

[glennmatthews]

[glennmatthews]

[glennmatthews]