This migrates the old single token file to the new token configuration file. The old token will be assigned to the default connection, or the one you use with the --connection switch when the old file is detected. If this is not correct, you will need to edit ~/.bugz_tokens and change the section name to match the appropriate connection. This is also related to #78.
The tokens are saved in ~/.bugz_tokens, which is a file that can be read by configparser. Each section in this file corresponds to a section in the configuration files. The token setting is the token passed back to us by Bugzilla's login command. This fixes #78.
Move the skip_auth test out of the login function and into the appropriate command functions. The attachment, get and search commands can work whether or not a user is logged in. On the other hand, the attach, modify and post commands require a login.
Document that these settings are used as defaults for search as well as post.
This allows default values for the product and component of a new bug to be set in the configuration files. This fixes #57.