Docs update

[pszulczewski]

Changes in NB2.0:

• Sites, Regions removed in favor of locations. name is not unique across locations, deletion needs extra care.
• Slug attribute removed in all models
• Device Roles, VLAN/Prefix Roles changes into generic Role type with content types.
• IPaddress creation doesn't support interface binding, extra endpoint has been created for that ip-address-to-interface.
• Various attribute names changed, look here for changes: https://github.com/nautobot/nautobot-ansible/pull/234/files#diff-6db24918e31bfe204d312fcef93775987be932ce8b3cdbb1dc9f2265caddbc26 this is nautobot_populate module to populate test data changes show diff between NB 1.X and 2.0.
• Namespaces added into IPAM, IPs/Prefixes/VLANS are enforced to be unique per namespace.
• Prefixes/VLANs don't relate directly with VRF anymore, but with namespace.
• Status is not Enum anymore, but dynamic. Needs to be queried like {"name": "Active"}

TODO:

• [x] Update docs for NB 2.0
• [x] Drop python 3.7