Add support for generating OAuth tokens

Jira uses OAuth 1.0 and requires that you manually authenticate the
jira-cards application before you can generate an OAuth token.  The Jira
application does not have a GUI for generating tokens.

This adds two commands, create-link and authorize, for creating the Jira
Application Link and generating OAuth access token respectively.

This code is pretty raw.  There's very little error checking or
verification.
Fix conflicts