virt: Added GithubIssues tool/module/class and example

This lays the foundations for some slick automated reporting and/or issue-manipulation.  It allows treating issues as if they were python list-indexes, and presents the data in an easily consumable, standardized, dictionary format.  The raw PyGithub objects are also accessible to support more advanced manipulations.

Note: Due to heavy, heavy, extra heavy caching requirements, this requires PyGithub version >= 1.13 which is newer than what you get with Fedora 18 :(  See example.py for more information.