Add section for command center

[FabioRosado]

Since the command center will allow users to toggle modules on/off and opsdroid web can be available to the public internet, we should make sure to implement #21 before adding this section. Only users with the token will have access to this section.

The command center section will have a few things:

• List of all modules found in the configuration
• List of stats from the /stats endpoint
• Possibility to add a new module