Removing Buildbot and Hercules CI systems

[zowoq]

Both of these CI systems will be disabled on the 1st October.

nixbot is the replacement for both of these systems.

• https://nixbot.nix-community.org
• https://nix-community.org/continuous-integration
• https://github.com/Mic92/nixbot

If anyone needs help moving their projects to nixbot feel free to ask me.