VIRA-293: Allow Personal Access Token (PAT) Auth

[jacobstr]

Personal access tokens authenticate via the 'Authorization: Bearer xxx' header. It looks like VIRA only supports basic auth at the moment.

Description of the feature is here: https://confluence.atlassian.com/enterprise/using-personal-access-tokens-1026032365.html

When using the python API, these creds can be provided via:

jir = JIRA(options={"headers": {"Authorization": "Bearer xxxx"}})

[n0v1c3]

VIRA-293 now has an active branch for anyone that would like to test this for me. I am working on other clean-up for the dev branch then it should all come together for a master push.