Add support for Nautobot REST API versioning in pynautobot

[glennmatthews]

We should add a user-friendly option for specifying the Nautobot REST API version to request:

• for all requests coming from a given api instance (i.e. as an initialization/configuration parameter on the Api class)
• for a specific request (i.e. as an optional parameter to the create(), get(), all(), etc. Endpoint methods, or (less ideally) as a setting directly on the api.http_session object).

Nautobot uses django-rest-framework's Accept-header versioning, so requesting a particular REST API version is a matter of specifying the appropriate HTTP header, such as Accept: application/json; version=1.3.

Supported API versions by Nautobot version:

Nautobot version	REST API version(s)
1.0	1.0
1.1	1.1
1.2	1.2
1.3	1.2 (default), 1.3 (if requested)

Additional references and information:

• Investigate and decide on REST API versioning approach nautobot#1465 for some background and discussion
• Implement REST API versioning and consolidate Job REST API endpoints nautobot#1521 for the pull request to implement API versioning in Nautobot