Remove dead/useless code; Re-implement GitHub processing

The old platform specific builder has been removed as it did not provide
any realistic direction to follow.

Alongside the old builder many GitHub processing classes went missing as
they were replaced with a more extensive event-driven system to support
plugins in the future as well as ease development of the bot.

The new GitHub processing system uses a binding map (read from a text
file, this could be improved) and Guava's EventBus to parse out the
incoming event context into the applicable GitHub API objects. The events
are then dispatched to be handled.

In addition to the massive amounts of GitHub changes, the choice of GitHub
API integration was switched from Eclipse's interface to a more versatile
system provided by Kohsuke. The new API library is also used in the GitHub
Jenkins plugin, proving that the library can withstand web hooks which are
a major part of this project's operation.